EP0752018A1 - Techniques de traitement de surface - Google Patents

Techniques de traitement de surface

Info

Publication number
EP0752018A1
EP0752018A1 EP95927112A EP95927112A EP0752018A1 EP 0752018 A1 EP0752018 A1 EP 0752018A1 EP 95927112 A EP95927112 A EP 95927112A EP 95927112 A EP95927112 A EP 95927112A EP 0752018 A1 EP0752018 A1 EP 0752018A1
Authority
EP
European Patent Office
Prior art keywords
substrate
coating
laser
carbon
technique
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP95927112A
Other languages
German (de)
English (en)
Other versions
EP0752018A4 (fr
Inventor
Pravin Mistry
Manuel C. Turchan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
QQC Inc
Original Assignee
QQC Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/241,930 external-priority patent/US5731046A/en
Application filed by QQC Inc filed Critical QQC Inc
Publication of EP0752018A1 publication Critical patent/EP0752018A1/fr
Publication of EP0752018A4 publication Critical patent/EP0752018A4/fr
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/26—Deposition of carbon only
    • C23C16/27—Diamond only
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24—Vacuum evaporation
    • C23C14/28—Vacuum evaporation by wave energy or particle radiation
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/26—Deposition of carbon only
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/10—Heating of the reaction chamber or the substrate
    • C30B25/105—Heating of the reaction chamber or the substrate by irradiation or electric discharge
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/04—Diamond

Definitions

  • the present invention relates to the surface treatment of substrates, for example metal substrates, the surface treatment including fabricating materials such as diamond and diamond- like carbon on the surface of the substrate.
  • the present invention relates to the fabrication of coatings such as diamond, diamond-like carbon (DLC) , Cubic Boron Nitride (CBN) , B 4 C, SiC, TiC, Cr 3 C 2 , TiN, TiB 2 , Si 3 N 4 and cCN, on substrates.
  • coatings such as diamond, diamond-like carbon (DLC) , Cubic Boron Nitride (CBN) , B 4 C, SiC, TiC, Cr 3 C 2 , TiN, TiB 2 , Si 3 N 4 and cCN
  • CVD processes Another disadvantage of CVD processes is that the cycle time is generally on the order of hours, for coating a limited number of parts. Generally, deposition rates are low, on the order of 1-l ⁇ m per hour (using hydrogen and methane precursors) . Other deposition processes, similar to CVD, are similarly limited.
  • Microwave (or microwave-plasma enhanced) CVD uses microwaves to excite the precursor gases, resulting in deposition rates of several microns per hour. Coatings deposited using this method tend to be of very high purity.
  • PVD Physical Vapor Deposition
  • the size of the substrate that can be coated is limited by the size of the vacuum chamber in which the process is carried out; the size of the substrate is typically less than eight inches in diameter. • inasmuch as these processes tend to rely primarily on a precipitation-type (i.e., generally directional deposition) mechanism, the "other" side of the substrate may exhibit shadowing or uneven deposition.
  • a precipitation-type i.e., generally directional deposition
  • FENG differs from the present invention, inter alia, in that the surface treatment technique of the present invention does not require first coating the substrate with a carbon-containing coating, the surface treatment technique of the present invention does not require a CVD process, and the surface treatment technique of the present invention advantageously employs laser energy to fabricate a coating on a substrate. FENG does, however, suggest that the "conventional" (i.e, accepted) method of applying a diamond coating to a substrate is to use a CVD process.
  • Carbide tungsten carbide grains in a cobalt binder
  • Various forms of carbide are known for tools and inserts, such as cobalt- consolidated tungsten carbide (WC/Co) .
  • cobalt in the substrate tends to present a problem when seeking to apply a diamond coating to a tool insert.
  • the cobalt binder phase found in carbide tools essentially "poisons" the diamond nucleation and growth process, resulting in formation of graphitic carbon rather than diamond (or DLC) .
  • a C0 2 gas laser beam is directed at normal incidence onto the surface to be coated. Movement between the substrate and the laser beam causes momentary heating of a very small area of the substrate surface with minimum energy input, resulting in a diamond deposit on the surface with almost no disturbance of the substrate.
  • DIAMOND-LIKE THIN FILMS which discloses applying a layer of a hydrocarbon molecule to a substrate by the Langmuir-Blodgett technique, and irradiating the surface with a laser to decompose the layer of molecules at the surface without influencing the substrate.
  • DIAMOND LIKE COATING AND METHOD OF FORMING discloses a method of depositing diamond-like films from a plasma of a hydrocarbon gas precursor.
  • the plasma is generated by a laser pulse which is fired into the gas and is absorbed in an "initiator" mixed with the gas.
  • the resulting detonation produces a plasma of ions, radicals, molecular fragments and electrons which is propelled by the detonation pressure wave to a substrate and deposited thereon.
  • This, and any technique like it is analogous to rain (diamond particles) falling on a pond (the substrate being coated) , and tends to result in a coating which is not adhered well to the substrate and which requires post- finishing to achieve a desired surface finish on the coated substrate.
  • THALER discusses the use of precursor gases such as a hydrocarbon, for example methane, ethane, propane, ethylene, acetylene, or similar hydrocarbon gases and vapors. This gas is cracked by intense heat to form a variety of high energy fragments, ions, radicals and free electrons. Cracking is achieved by subjecting the hydrocarbon to intense laser pulses, for example, C0 2 laser having a 50 nanosecond spike and a power output of 10 watts/cm 2 .
  • precursor gases such as a hydrocarbon, for example methane, ethane, propane, ethylene, acetylene, or similar hydrocarbon gases and vapors. This gas is cracked by intense heat to form a variety of high energy fragments, ions, radicals and free electrons. Cracking is achieved by subjecting the hydrocarbon to intense laser pulses, for example, C0 2 laser having a 50 nanosecond spike and a power output of 10 watts/cm 2 .
  • THALER discusses the user of an "initiator" which is mixed with the hydrocarbon gas or vapor.
  • the initiator is preferably a compound which is strongly absorbing at the output wavelength of the laser impulse used.
  • the output wavelength for a C0 2 laser is 10.6 microns ( ⁇ m)
  • sulfur hexafluoride (SF 6 ) is a highly effective initiator when used with such a laser, providing both sulfur and fluoride ions and radicals upon detonation.
  • the initiator serves to accumulate the applied (laser pulse) energy, in a very small volume, releasing same explosively, fragmenting the hydrocarbon into highly reactive ions and radicals, and imparting high translational energy to the formed gases.
  • the coating resulting from these detonations will have properties of both diamond and fluorocarbons.
  • GAVIGAN discusses the use of other lasers, including a continuous wave YAG laser, and a pulsed C0 2 , YAG or excimer laser. Generally, as the laser scans over the surface of the substrate the melted area not (no longer) under the laser beam is rapidly solidified due to the heat absorption of the unmelted substrate. GAVIGAN discusses that the process will work with other alloys of titanium that contain other strong nitride formers in their composition, such as vanadium, columbium, carbon and aluminum.
  • GAVIGAN is gratuitously cited herein, without prejudice, as representative of performing other processes (i.e., than forming coatings), on other (i.e, other than steel) materials, with lasers, although its teachings would appear to be limited to producing a crack-free nitride-hardened surface on titanium and its alloys.
  • USP 5.066.515 (“OHSAWA”: 11/91: 427/53.1) discloses a method of forming an artificial diamond comprising applying a laser beam to a glassy solid carbon material while moving a point on the glassy solid carbon material at which the laser beam is applied, to form a locally fused portion thereon, whereby every part of the locally fused portion is cooled as the point moves away therefrom. During cooling of the locally fused portion, an artificial diamond is formed in adjacent regions on both sides of the solidified locally fused portion;
  • USP 4.987.007 f'WAGAL 1/91; 427/53.1 discloses producing a layer of material on a substrate by extracting ions from a laser ablation plume in a vacuum environment.
  • the apparatus includes a vacuum chamber containing a target material and a laser focused on the target to ablate the material and ionize a portion of the ablation plume, and is suitable for forming diamond-like carbon films on a clean, unseeded silicone substrate.
  • the process can produce a DLC layer of exhibiting uniform thickness with less than 3% variation at a rate of 20 ⁇ per hour.
  • USP 4.522.680 (“OGAWA”: 1/85: 156/624) discloses a method of producing diamond crystals comprising providing a pressure- resistant body having a nucleus of a starting material being crystallized in the inside thereof. The nucleus is applied with an energy which is capable of passing through the pressure- resistant body and being absorbed by the starting material, by which the nucleus is heated and melts. The melt is then gradually cooled under pressure to form crystals. A laser beam or high frequency induction heating technique is used for heating the nucleus.
  • USP 5.176.788 (“KABACOFF” ; 1/93; 156/603). entitled METHOD OF JOINING DIAMOND STRUCTURES, discloses the use of pulsed laser light to join diamond structures together.
  • the second output beam is used to anneal the deposited (on the substrate) film (of condensed material) .
  • the process is especially useful for advanced electronic device applications, especially for incorporating films into silicon integrated circuit structures.
  • the 1550 cm * peak is due to graphite, the sensitivity of which is about two orders of magnitude higher than that of diamond.
  • Diamond-like carbon (DLC) always exhibits these two peaks (1332 cm '1 and 1550 cm *1 ) . Due to the sensitivity factor, it has generally been accepted that the 1332 cm *1 peak is adequate proof of the existence of diamond material in a sample.
  • many synthetic diamond materials do not exhibit this peak at all, exhibiting instead tiny broad features superimposed on significant background luminescence.
  • the sensitivity (sharpness) of the diamond peak may depend to a certain degree on its grain size - namely, the smaller the grains, the lower the sensitivity and the broader the peak will be.
  • Stereolithography is a process by which three dimensional objects are fabricated from thin layers of hardened cured liquid polymers.
  • Current rapid prototyping systems make an object by selectively hardening or cutting layers of material into a shape defined by CAD data.
  • CAD data typically, ultraviolet, argon-ion, or other type of laser is used harden the polymer.
  • the CAD data mathematically represent the shape of the object to be produced as a series of sequential thin layers.
  • a desired composite material such as diamond, DLC, Cubic Boron Nitride (CBN) , B 4 C, SiC, TiC, Cr 3 C 2 , TiN, TiB 2 , Si 3 N 4 and cCN, niobium, carbide, titanium nitride, aluminum nitride, etc.
  • energy such as three distinct laser beams from three distinct lasers are directed at the surface of a substrate to treat the surface of the substrate.
  • the process parameters and interactions of the three lasers are controlled to achieve a desired effect on and/or below the surface of the substrate.
  • the process parameters include: • the wavelength of each laser;
  • the operating mode e.g. , pulsed, super-pulsed or continuous wave
  • the output power of each laser
  • one or more constituent (native) elements disposed in a sub-surface region of the substrate may be mobilized, at corresponding one or more rates, and moved towards the surface of the substrate to produce a concentration gradient of the one or more constituent elements in a sub-surface zone. Further, selected amounts of a selected portion of the constituent elements may be separated and vaporized in a controlled manner.
  • the one or more constituent elements of the substrate are considered to be a "primary" source of material for the process.
  • a first of the three lasers is an ultraviolet laser, such as a pulsed excimer laser, operating at either 192nm, 248nm, or 308nm, with a power output of tens of (0-200) watts (W) , with a pulse energy of up to 500 mJ (millijoules) , a pulse length of up to 26 nanoseconds (ns) , and a repetition rate of up to 300 Hz (Hertz);
  • a pulsed excimer laser operating at either 192nm, 248nm, or 308nm, with a power output of tens of (0-200) watts (W) , with a pulse energy of up to 500 mJ (millijoules) , a pulse length of up to 26 nanoseconds (ns) , and a repetition rate of up to 300 Hz (Hertz);
  • a second of the three lasers is a Nd:YAG laser, operating at 1.06 microns in a continuous (CW) or burst mode, or Q-switch with a power output of hundreds of (0-1500) watts, with a pulse energy of up to 150 J (Joules) , a pulse frequency of up to 1000 Hz, a pulse length of up to 20 milliseconds (ms) , and (in a pulse/burst mode) a pulse stream duration of up to 5 seconds;
  • a third of the three lasers is a C0 2 laser operating at a wavelength 10.6 microns, with a output power on the order of 500-10000 W, a pulse frequency up to 25 Khz, a pulse up to 25 microseconds, a super-pulse frequency up to 20 Khz, and a super- pulse width up to 500 microseconds.
  • the resulting diamond coating thickness "t" is approximately 3 mm (or approximately three times the depth of the conversion zone) .
  • the surface treatment technique of the present invention is applicable to treating any of a number of substrates, including metal and non-metal substrates (non-metal substrates include ceramics and polymeric substrates) .
  • Specific materials that can be treated, or introduced into the reaction system include, but are not limited to: • metals (B, Al, Ti, Nb, Ta, Cr, Mo, W, Re, etc.);
  • Figures 10A, 10B, IOC and 10D are graph, chart and graph, respectively, of operating parameters for an excimer, Nd:YAG and C0 2 laser, according to an embodiment of the present invention.
  • Figure 19 is a partial cross-sectional view of an alternate apparatus suitable for introducing secondary element into the reaction system.
  • the coating technique of the present invention involves extracting and reacting a "constituent" (or “primary”) element from the substrate, reacting it in a “reaction zone" immediately above the surface of the substrate, optionally introducing a “secondary element” from a “secondary source” to augment the reaction, and diffusing a "composite material” (the reacted material, having its physical structure, -including phase, altered, modified, changed, and/or that has had another one or more elements added to it) back into the substrate.
  • a "composite material” the reacted material, having its physical structure, -including phase, altered, modified, changed, and/or that has had another one or more elements added to it
  • Step B the composite material is diffused into the surface of the substrate creating a "conversion zone" extending into the substrate from the surface of the substrate.
  • This is essentially a process of passive diffusion from a greater concentration of composite material in the PGR to a lesser concentration of composite material in the substrate.
  • the process next proceeds in one of two directions (Steps C and D, described hereinbelow) .
  • the process can be stopped, at the point of having successfully formed a conversion zone exhibiting a controlled concentration of composite material.
  • the composite material in the conversion zone may be diamond or DLC.
  • the production of a composite material, and its diffusion into the conversion zone does not alter the volume of the substrate.
  • the conversion zone can further be treated by repeating the steps of mobilizing, vaporizing and reacting (in a manner similar to Step A) the composite material within the conversion zone, or mobilizing, vaporizing and reacting the one or more of the constituent elements from the substrate, or both.
  • the process acquires synergy and will proceed at a greatly increased rate (e.g. exponentially) . This process is iterated to achieve any desired concentration of composite material at the surface of the substrate, and any desired gradient of composite material within the conversion zone.
  • a coating can be fabricated on the surface of the substrate.
  • the coating, or fabricated material can have an entirely different chemistry than that of the conversion zone.
  • a secondary source may (Step E) or may not (Step F) be introduced to the system.
  • a "secondary” source (the substrate itself is considered the “primary” source) is activated to introduce one or more "secondary” elements (the one or more constituent elements of the substrate are considered to be “primary” elements) to the reaction system.
  • the energy source is used, in this case, to fabricate a synthesized coating composition (such as diamond or diamond-like carbon) on the surface of the substrate.
  • the synthesized coating composition is a fabricated material containing both the one or more secondary elements and the composite material, which may be the same as one another or different than one another.
  • the primary conversion zone could be approximately 0.75 mm deep, and the secondary conversion zone could be approximately 0.25 mm thick.
  • Step F in a process Step F, wherein a secondary source is not introduced to the system, a small amount of the composite material from the conversion zone is mobilized, vaporized and reacted (in a manner similar to the Step A) to form a secondary conversion zone below the substrate, which can further be reacted (by the energy source) to form a coating on the substrate.
  • a coating being fabricated on the substrate which is likely to be thinner than the coating that was fabricated using a secondary source (Step E) . It is, however, entirely possible that there will be a sufficient amount of constituent element available in the substrate itself to fabricate a relatively thick coating on the surface of the substrate in the Step F.
  • the energy source will cause the tungsten and the carbide to disassociate into tungsten and carbon form, and the carbon will be the constituent element ("native" source) for fabricating a diamond or DLC coating on the substrate.
  • dissolved carbon in the cobalt matrix also provides a "native" source of carbon for the fabrication of diamond or DLC coating.
  • the surface treatment technique of the present invention is superior to prior art CVD (and PVD) processes in that in those processes cobalt will exhibit an undesirable graphite- forming influence in the system which will "poison" the system and inhibit the formation of a diamond coating or DLC coating.
  • Step G (which follows Step E in the process flow)
  • a different (than the previously used) secondary source having different one or more secondary elements can be introduced to the reaction system. This will result in a multi-layer coating being fabricated on the substrate.
  • an overlying coating (layer) of titanium carbide can be fabricated, over which a layer of titanium nitride can be fabricated, over which a layer of diamond can be fabricated, by sequencing the introduction of secondary elements into the reaction system.
  • a thick diamond coating could be overcoated with a thin coating of cubic Boron Nitride (CBN) .
  • CBN cubic Boron Nitride
  • the process is also suitable for fabricating a coating of diamond on silicon nitride.
  • the process can also be employed to fabricate a composite structure of diamond and CBN, or vice-versa, or to fabricate a composite structure of diamond particles mixed with silicon carbide or silicon nitride.
  • Step A the process flow can proceed directly from the initial mobilizing, vaporizing and reacting (Step A) to the step (Step E) of introducing a secondary source to the reaction system.
  • Step E the step of introducing a secondary source to the reaction system.
  • the step of mobilizing, vaporizing and reacting the titanium from the substrate will serve to form a diffusion bond with the subsequently fabricated diamond or DLC coating.
  • carbon can be introduced by the secondary source to produce silicon with silicon carbide in the conversion zone.
  • the silicon carbide can be converted to diamond.
  • nitrogen can be introduced by the secondary source to produce silicon with silicon nitride in the conversion zone and, if desired, the secondary source can be sequenced to provide carbon in the reaction system for forming a diamond or DLC layer over the conversion zone.
  • FIG. 2A shows a cross-section of an exemplary treated substrate 200 that has been treated according to the techniques of the present invention, according to one or more of the process steps described with respect to Figure 1. .
  • a substrate 202 having a top surface 204, a secondary conversion zone 206 formed below the surface of the substrate, a primary conversion zone 208 formed underneath the secondary conversion zone 206, and a coating 210 that has been fabricated on the surface of the substrate.
  • the treated substrate 200 could result, for example, from performing the process Steps A, B, D and E (of Figure 1) .
  • the secondary conversion zone 206 will have a thickness (d2) typically less than the thickness (dl) of the primary conversion zone, and will exhibit a greater concentration of composite material than the primary conversion zone.
  • the thickness of the fabricated coating is "t".
  • FIG. 2B shows a cross-section of an exemplary treated substrate 220 that has been treated according to the techniques of the present invention, according to one or more of the process steps described with respect to Figure l.
  • a substrate 222 having a top surface 224, a first coating layer 226 of thickness "tl" formed atop the substrate surface (the primary conversion zones and secondary conversion zones are omitted from this figure, for illustrative clarity) , a second coating layer 228 of thickness "t2" formed atop the previous (as viewed) surface of the first coating layer 226, and a third coating layer 230 of thickness "t3" formed on the top (as viewed) surface of the second coating layer 228.
  • Such a treated substrate 220 could result, for example, from performing the process steps A, B, D, E and G (of Figure 1) .
  • a multi-layer coating such as is shown in Figure 2B is readily fabricated.
  • the first coating layer 226 can be formed from a combination of a constituent element of the substrate and a first secondary element introduced into the reaction system by the secondary source
  • the second coating layer 228 can be formed from a combination of a constituent element of the first coating layer 226 and a second secondary element introduced into the reaction system by the secondary source
  • the third coating layer 238 can be formed from a combination of a constituent element of the second coating layer 226 and a third secondary element introduced into the reaction system by the secondary source.
  • any number of layers can be fabricated, having a predetermined material composition.
  • FIG. 3 illustrates, schematically, the operation of a surface treatment system 300, according to the present invention.
  • Three separate and distinct lasers 312, 314 and 316 each direct a beam, via a respective beam delivery system (BDS) 322, 324 and 326 onto a surface 304 of a substrate 302.
  • BDS beam delivery system
  • the beams are directed to converge on a selected area 330 of the substrate, indicating that selected areas (each less than the entire surface) of a surface of a substrate can be treated.
  • the selected area (330) In order to treat the entire surface of the substrate, either (a) the selected area (330) must be equal to or greater than the total surface area of the surface of the substrate, or (b) a mechanism must be provided for causing relative motion between the substrate and the beams, to "scan" the selected treatment area across the entire surface of the substrate.
  • the substrate can be moved relative to the beams, in the direction indicated by the arrow 332, thereby causing the selected area whereat the beams converge to move in an opposite direction indicated by the arrow 334 to surface treat an area greater than one selected area of the substrate.
  • the substrate 302 may be held in a positioning mechanism, such as in the end effector (e.g., x,y,z) of a multi-axis robot, in which case it will be possible to move the substrate in any of the x, y and z directions, which is useful for treating substrates of complex geometry and/or multiple surfaces of a substrate.
  • a positioning mechanism such as in the end effector (e.g., x,y,z) of a multi-axis robot, in which case it will be possible to move the substrate in any of the x, y and z directions, which is useful for treating substrates of complex geometry and/or multiple surfaces of a substrate.
  • a simpler mechanism such as with an x-y positioning table.
  • One advantage of using a robot-type mechanism for imparting motion to the substrate is that the same robotic mechanism can be used to pick (retrieve) substrates for surface treatment and to place (deliver) substrates after surface treatment.
  • the same robotic mechanism can be used to pick (retrieve) substrates for surface treatment and to place (deliver) substrates after surface treatment.
  • movement of the substrate can be effected under computer control, and programmed so that the beam will follow any desired path, dwelling on any portion of the area of the surface of the substrate for any desired time.
  • the laser energy sources 312, 314 and 316 can be focussed, diffused, converged, diverged, transported, or the like by interposing suitable known optical elements for achieving these functions in the path of the beam and which may be controlled by a computer numerical control.
  • suitable known optical elements for achieving these functions in the path of the beam and which may be controlled by a computer numerical control.
  • Such optical elements are generally shown as beam delivery systems (BDS) 322, 324, 326.
  • a first one 312 of the lasers is used to vaporize the constituent element (create a gas phase) , and to break chemical bonds in the vaporized constituent element.
  • the first one of the lasers is preferably an excimer laser operating, for example, at 192, 248 or 308 nm (nanometers) .
  • Such excimer lasers are useful for vaporizing any of a number of constituent elements.
  • the excimer laser will take a sole or primary (lead) role in causing the constituent element to vaporize, and in initiating the preliminary gas reaction (PGR) above the surface of the substrate.
  • PGR preliminary gas reaction
  • the excimer laser will be supported in these roles by another one (e.g., 314) of the lasers.
  • a second one 314 of the three lasers is used, primarily, to drive the diffusion function (e.g.. Step B) , and also balances the thermal gas reaction and the stoichiometric chemistry of the gas phase reactions.
  • This laser is preferably a Nd:YAG laser, and normally assumes a supportive role (in a manner of speaking) to the lead role of the excimer laser.
  • the Nd:YAG laser will also aid in vaporizing the constituent component, especially in the context of bright (reflective) materials, and in some instances the Nd:YAG laser will assume the lead role and be supported by the excimer laser (i.e., for some substrate and desired coating materials, the roles of the excimer and Nd:YAG lasers may be interchanged) .
  • the excimer laser i.e., for some substrate and desired coating materials, the roles of the excimer and Nd:YAG lasers may be interchanged
  • the two lasers that keeps the reaction mechanism balanced out.
  • the lasers are shown in Figure 3 as directing their respective beams onto the selected area 330 of the substrate from different angles (an converging on the spot 330) , it is within the scope of the present invention that the beams could be directed coaxially at the reaction zone. Generally, due to the synergy effected by the three lasers, they should all be directed at the same spot (330) on the substrate.
  • FIG. 4 illustrates a surface treatment system 400 particularly suited to introducing one or more secondary elements.
  • the three lasers e.g., the three lasers 312, 314, 316 of Figure 3
  • BDS beam delivery system
  • the beams are directed at a selected area 430 (compare 330) of a surface 404 (compare 304) of a substrate 402 (compare 302) , and relative motion between the beam(s) and the substrate 402 is indicated by the arrows 432 and 434 (compare 332 and 334).
  • SECONDARY SOURCE 1 secondary source
  • the one or more secondary sources introduce corresponding one or more secondary elements into the reaction system (constituent elements of the substrate are considered to be primary sources for the reaction) , and the secondary elements may be in the form of a gas, a vapor, a powder, or other suitable form, to augment the reaction occurring in the reaction zone immediately above the surface of the substrate.
  • the secondary element is suitably provided by a nozzle (jet) adequate to direct a stream of the secondary element at the reaction zone, so that the secondary element(s) can contribute to the reaction that is being driven by the laser beams.
  • the secondary element(s) be directed towards the same area (430) of the substrate whereat the laser beams are directed, but it is also possible to introduce the secondary source at another selected area on the substrate, or to simply "flood" the substrate (i.e., the entire surface of the substrate) with the secondary element(s).
  • a coating may be fabricated on the surface of the substrate, for example, as described with respect to Step E in the process flow diagram of Figure 1.
  • the secondary element is introduced into the reaction system by any of a number of known means, such as by spraying, dispersing, depositing, ablating, or any other known means, and may be in the any suitable form such as a liquid, a gas, a solid, a plasma, a powder, or the like.
  • a gaseous secondary element may be introduced into the reaction system using a pressurized nozzle (jet) that is designed to deliver the gaseous secondary element in an envelope of another (e.g., inert) gas which will focus (direct) the delivery of the secondary element by helically-controlled swirling of the gases exiting the nozzle (jet) .
  • the secondary element can be directed to the same selected area of the substrate as the incident energy beam.
  • the gaseous secondary element (SS) and the enveloping (shielding) gas (SG) can both serve as secondary elements in the reaction.
  • the secondary element may also be selected to serve as a "shield" (from the environment, without necessitating the use of a vacuum) for the process when a secondary source is not needed (see, e.g., steps C, F and H in the process flow, described hereinabove) , in which case the secondary element (and the enveloping gas) may be a clean or inert gas. Depending on the treatment, a shielding function may not be necessary.
  • Figure 5 illustrates an embodiment of a nozzle 500 suitable for introducing a gaseous secondary element (from a secondary source) to the reaction system.
  • the nozzle 500 is suitable for introducing three distinct gases - a gaseous secondary element (SS) , a shielding gas (SG) and a "buffer" gas (BG).
  • SS gaseous secondary element
  • SG shielding gas
  • BG buffer gas
  • the nozzle 500 is annular, having a ring-like body portion 508 and central axial opening 506.
  • the nozzle 500 is disposed above a surface of a substrate (SUBSTRATE) undergoing treatment.
  • the three laser beams El, E2 and E3 may be directed through the central opening of the nozzle, at the substrate.
  • a shielding gas such as nitrogen
  • SG lower (closest to the surface of the substrate) inlet 530 of the nozzle
  • SS secondary source
  • SS is introduced through an intermediate inlet 520 of the nozzle, circulates through a annular runner 522 throughout the body of the nozzle, and is ejected via outlet ports 524 to the central opening of the nozzle.
  • the secondary source Since the secondary source is ejected above (as viewed) the shielding gas, it is in a position to be reacted by the laser energy (El, E2, E3) , and to be enveloped (surrounded) by the shielding gas.
  • a buffer gas (BG) analogous to a sensitizing agent, may be introduced in conjunction with, such as above (as viewed) the secondary source.
  • the buffer gas is selected (if necessary) to assist in the transferring energy from the laser beams to the secondary source, and may act as a buffer in breaking down the secondary source.
  • the buffer gas is introduced through an upper inlet 510 of the nozzle, circulates through a annular runner 512 throughout the body of the nozzle, and is ejected via outlet ports 514 to the central opening of the nozzle. Since the buffer gas is ejected from the nozzle above (as viewed) the secondary source, it is in a position to absorb laser energy (El, E2, E3) for subsequent transfer to the secondary source gas.
  • the nozzle 500 is disposed at a distance "h" above the substrate, which is established to provide sufficient time (i.e., propagation rate times distance) for the gas reaction to substantially complete itself between the nozzle and the substrate.
  • Figures 5A and 5B illustrate an alternate, preferred (e.g., for fabricating a diamond coating on a tungsten carbide substrate) embodiment of a nozzle 550 for delivering a secondary source (SS) gas and a shielding gas (SG) to the treatment system, and is generally similar to the embodiment 500 shown in Figure 5 in that the nozzle is annular and has a central opening through which the laser beams (shown by the single arrow labelled "BEAMS", in Figure 5B) can be directed through the gases towards the surface of the substrate (not shown) being surface treated.
  • the nozzle 550 is constructed as a "sandwich" of two flat, annular nozzle bodies 552 and 554, disposed one (552) atop the other (554).
  • the top nozzle body 552 has an inlet 561 for receiving the secondary source (SS) gas, an annular runner 562 for circulating the secondary source gas evenly (in a fluid dynamic sense) throughout the top nozzle body, and a plurality of outlet ports 564 disposed about the inner diameter (ID) of the nozzle body 552.
  • the outlet ports are directed tangentially, with respect to the axis of the nozzle body, to impart a swirling motion (e.g. , clockwise, as viewed in Figure 5A) to the ejected secondary source gas.
  • the secondary source gas is preferable ejected from the nozzle body 552 flat (coplanar) with respect to the nozzle.
  • the nozzle 550 is disposed at a sufficient distance ("h", see, e.g., Figure 7) above the surface of the substrate to permit the sought after reaction of the secondary source to occur.
  • the shielding gas (SG) is introduced through an inlet 580 in the lower nozzle body 554, circulates in a runner 582 throughout the lower nozzle body 554, and is ejected via a plurality of outlet ports 584 to the opening in the nozzle body.
  • the openings in the two nozzle bodies 554 and 552 are concentric, and preferably of the same size as one another.
  • the outlet ports 584 for the shielding gas are directed downwards (as viewed) , towards the substrate being treated.
  • the outlet ports 584 should also be directed tangentially, with respect to the axis of the nozzle body, to impart a swirling motion (e.g., clockwise, as viewed in Figure 5A) to the ejected secondary source gas. This results in a "whirling vortex" (represented by the line 590) of shielding gas which will envelope and direct the secondary source towards the substrate.
  • the runners 562 and 582 are formed as troughs extending into the lower (as viewed) surfaces of the respective nozzle bodies.
  • the top surface of the lower nozzle body 554 closes off the trough (runner 562) in the upper nozzle body 552, and a simple annular plate 592 having a central opening closes off the trough (runner 582) in the lower nozzle body 554.
  • substrates will benefit from preparation of the surface sought to be coated. Grinding marks and contaminants may be present on the surface, and should be removed. Polishing and chemical etching are known processes for performing pre- treatment. Generally, chemical etching of a substrate requires the handling of hazardous chemicals, and result in toxic waste, each of which introduces added complexity to a system for coating a substrate. Moreover, each substrate composition would require its own chemicals to perform such etching. According to the present invention, substrates of various types are prepared for fabrication of a coating using the same laser(s) that are already in place for fabricating coatings.
  • the surface treatment system (e.g., 300) can be used not only for performing the surface treatment on the substrate, but can also be used to perform pre-treatment. Generally, this is a matter of controlling the process parameters of the lasers, vis-a-vis the gases.
  • Figures 6A and 6B illustrate how a substrate can be pre- treated, in conjunction with the surface treatment process of the present invention.
  • the pre-treatment process can be performed prior to (i.e., separately from), or in conjunction with, the surface treatment process described with respect to Figure l.
  • the pre-treatment technique of the present invention can be used as a "precursor" to characterize the surface of a substrate for any subsequent coating process, including CVD and the like.
  • a tungsten carbide substrate 602 will exhibit grains 630 of
  • surface chemistry changes can be induced in such substrates, if required.
  • the chemistry of a tungsten carbide substrate can be altered to exhibit stable cobalt nitride.
  • substrate is pre-treated by using a one of the lasers (e.g., the excimer laser) to ablate cobalt (as well as some tungsten carbide) from the surface of the substrate, thereby exposing the tungsten carbide grains 634, and performing other significant metallurgical functions described in greater detail hereinbelow.
  • a one of the lasers e.g., the excimer laser
  • cobalt as well as some tungsten carbide
  • the cobalt can also be reacted to form a stable cobalt nitride.
  • the cobalt can be ablated and some WC and Co can also be reacted to form stable carbon nitride or cobalt nitride.
  • Nitrogen can be introduced to form cobalt nitride, if desired, during pre-treatment, to change the surface chemistry of the
  • Figure 6B represents a tungsten carbide substrate (602) that has been pre-treated and, as shown therein, the pretreatment process will also result in a desirable rounding off of the peaks of the tungsten carbide grains.
  • Cobalt can be minimized or eliminated front the surface, grinding marks and impurities can be removed from the surface, and the structure of the exposed tungsten carbide can be controlled and modified.
  • the subsequent surface treatment process can much better be controlled, by imparting known (e.g., constant, repeatable) characteristics to the surface of the substrate being treated.
  • a sub-surface region extending to a depth d' , has been cleared of cobalt.
  • Figures HA and HB, described hereinbelow are also descriptive of the pre ⁇ treatment process. Additional detail of the process parameters is set forth in the examples described hereinbelow.
  • the pre-treatment process of the present invention effects metallurgical changes within the surface of the substrate.
  • diamond having a 1,0,0 (100) crystal orientation can be formed, which will serve as a highly desirable nucleation site for subsequently fabricated diamond (or DLC) coating on the surface of the substrate.
  • this is irrespective of the technique used to coat the substrate, and is useful for CVD processes and the like.
  • the pre-treatment process of the present invention advantageously forms a complex of carbon + nitride + cobalt- nitride or prescribed orientation in the valleys between the tungsten carbide peaks which is highly suitable for subsequent coating (or for simultaneous fabrication of a coating) .
  • Figure 7 illustrates a complete surface treatment system 700, suitable for performing the entire repertoire of process steps outlined in Figure 1, utilizing the three laser process described with respect to Figure 3, including introducing one or more secondary sources as discussed with respect to Figure 4, incorporating a preferred nozzle design such as was described with respect to Figures 5A and 5B, and suitable for performing the pretreatment described with respect to Figures 6A and 6B.
  • the surface treatment system 700 includes three lasers: an ultraviolet excimer laser (LASER 1) 712, an infrared Nd:YAG laser (LASER 2) 714 and an infrared C0 2 laser (LASER 3) 716.
  • Each laser emits a beam which is directed through the opening of the nozzle 722 towards the surface of the substrate 702.
  • the nozzle 722 has an axis 723 which is preferably normal (at 90°) to the surface of the substrate 702.
  • the excimer laser 712 is directed, at a first angle " ⁇ l", towards the surface of the substrate.
  • the Nd:YAG laser 714 is directed, at a second angle " ⁇ 2", towards the surface of the substrate.
  • the C0 2 laser 716 is directed, at a third angle " ⁇ 3", towards the surface of the substrate.
  • the first angle ⁇ l 0° (parallel to the axis of the nozzle)
  • the second angle ⁇ 2 -30°
  • the third angle ⁇ 3 +30°.
  • the nozzle 722 is disposed at a standoff distance "h" above the surface of the substrate 702.
  • a gaseous secondary source (SS) 720 e.g., a carbon- containing gas, such as carbon dioxide
  • a shielding gas (SG) 724 a non-reactive or inert gas, such as nitrogen, helium, argon, or the like
  • the three laser beams are directed through the nozzle to converge on a selected area of the substrate 702, in the manner discussed hereinabove with respect to Figure 3.
  • the three laser beams are sized so that each beam completely covers the surface of the substrate (the selected area encompasses the entire surface of the substrate) .
  • the substrate is a rectangular substrate, having dimensions "X" and "Y", and is moved (arrow 732) during surface treatment in the y-axis.
  • a plasma (not shown in this figure, see Figure 8) is formed beneath (as viewed) the nozzle, immediately atop the surface of the substrate 702.
  • the secondary source is converted in the plasma, along with vaporized constituent elements, to fabricate a coating on the surface of the substrate.
  • the role of the excimer laser 712 is to perform surface ablation, break down the secondary source (SS) and initiate synthesis for bonding and growth (fabrication) of a coating on the surface of the substrate;
  • the Nd:YAG laser 714 assists the excimer laser in breaking down the secondary gas and performs a prominent role in diffusion;
  • the C0 2 laser 716 helps maintain the thermal balance of the reaction, both in the plasma and on the substrate.
  • Figure 8 illustrates apparatus for supporting a substrate 802 being treated, and a preferred shape of the plasma (“PLASMA”) being generated in the surface treatment process.
  • PLASMA a preferred shape of the plasma
  • a distinct advantage of the present invention is the ability to form a flat plasma that is closely adjacent the surface of the substrate being treated. Moreover, such a flat plasma can wrap around the corners of the substrate, and is advantageous in the fabrication of coatings on round tools such as drills. Generally, the plasma "delivers" secondary elements to the surface of the substrate, and ensures localized (versus) mass heating of the substrate.
  • the substrate 802 is disposed atop a pedestal 804 which has a button-like projection 808 extending upward from its top (as viewed) surface.
  • the projection 808 is preferably smaller in area than the substrate being supported, and the substrate is disposed concentrically atop the projection.
  • a vacuum passage 810, passing through the pedestal 804 is suitable for "chucking" (holding) the substrate onto the pedestal, and is well suited to automated handling of substrates in a production environment.
  • the plasma shown in Figure 8 created by a surface treatment system such as was described with respect to Figure 7, is a "flat" plasma, in that it is generally coplanar with the surface of the substrate, and is of controlled, minimal, vertical (as viewed) extent.
  • a flat plasma reactions of vaporized constituent elements (from the substrate) and secondary elements (from secondary sources) can be well controlled, and localized at the surface of the substrate which is intended to be treated.
  • the flat (squat) plasma shape, and its intimate contact with the surface of the substrate, is advantageous in that it allows for fabrication (growth) of a coating directly on the surface of the substrate.
  • the flat plasma interacts with the surface of the substrate. This is in marked contrast to CVD systems, and plasmas shaped like tall columns, the coating is "rained" down onto the surface of the substrate. and allows for relatively high coating rates of coating fabrication.
  • a significant advantage of the invention accrues to the flat plasma that can be formed, and vacuum chucking complements the formation of such a flat plasma.
  • the plasma generated by the process of the present invention can be caused to wrap around the edges of the substrate being treated.
  • Such wrapping around (the edges of the substrate) of the plasma can be enhanced by providing a plurality of auxiliary vacuum passages 812 through the pedestal, such that these passages exit the top surface of the pedestal outside of the projection 808 yet within the area underneath the substrate.
  • the same (or another) vacuum which serves to hold the substrate onto the pedestal will serve to augment (enhance) wrapping of the plasma around the edge of the substrate.
  • reaction mechanisms effected by the combination of lasers and plasma can be classified as “pyrolitic” and “photolytic”.
  • the laser(s) serve(s) to:
  • the laser energy is absorbed by the reactant, which is initially excited into non-dissociative states. After energy relaxation, the reactant gas can dissociate to form thin films,
  • the laser(s) serve(s) to dissociate gas-phase or surface-adsorbed molecules to form deposit atoms or intermediates without significantly heating the gas or surface of the substrate.
  • Laser excitation could occur by stimulating electronic transitions by the absorption of one ultraviolet photon or, alternatively, by the absorption of several visible or ultraviolet photons. In the latter case, absorption may occur either in a concerted manner, as in multiphoton absorption, or in a sequential manner which may, in fact, involve photon absorption by intermediate products.
  • the photolytic products may further be decomposed by the pyrolitic process.
  • the output of an excimer laser can effectively be absorbed by carbon dioxide (e.g. , from the secondary source) , which leads photochemical reactions to break down C-O bonds to form diamond films or reactive intermediates.
  • carbon dioxide is essentially transparent to the output of an Nd:YAG laser
  • the Nd:YAG laser output is mainly absorbed by the reaction intermediate created by the excimer laser, and by the substrate or by some film overlaying it.
  • Figure 9 illustrates, schematically, an overall surface treatment system 900 (similar to the system 700) .
  • a substrate 902 is disposed underneath a nozzle (omitted from this view, for illustrative clarity)
  • energy from lasers 910 is directed at the substrate to create a reaction within the surface of the substrate and immediately above the surface of the substrate (including forming a flat plasma)
  • one or more secondary elements are introduced from one or more secondary sources 920 to augment the reaction occurring at the substrate
  • the substrate can be moved around by a multi-axis positioning mechanism 930 (e.g., a multi-axis robot), and the operation of these components is controlled by a controller 940 (such as a suitably programmed computer) .
  • the system can exercise control over the timing (e.g., sequence of turning on and off) of the lasers (910) , as well as the relationship between pulses delivered by the various lasers.
  • a system for fabricating a coating on a substrate comprises three lasers, each with its own beam delivery system (BDS) , employs a nozzle delivering a secondary source (SS) in an envelope of a shielding gas (SG) , and creates a flat plasma on the surface of the substrate.
  • BDS beam delivery system
  • SS secondary source
  • SG shielding gas
  • the substrate may be pre-treated for subsequent coating by any suitable technique for forming a coating on a substrate, including the techniques of the present invention, or an entire surface treatment process may be performed including a pre ⁇ treatment regime and a coating regime.
  • a flat carbide cutting tool insert substrate is pre-treated, or is treated (pre-treated and coated) to have a diamond (or DLC) coating.
  • a diamond (or DLC) coating For simplicity, it is assumed that the entire substrate is treated at once (i.e., the beams are of sufficient dimension to "flood" the entire surface area of the substrate) .
  • a surface treatment system such as was described with respect to Figures 7 and 9 is employed.
  • Figure 10 is a process timing diagram illustrating the process of pre-treating a substrate for subsequent fabrication of a coating (or deposition of a coating by a CVD process, or the like) .
  • Figure 10A is a process timing diagram illustrating the process of simultaneously (in-situ) pre-treating a substrate and fabricating the coating.
  • Figure HA is a photomicrograph illustrating the surface of a tungsten carbide cutting tool insert (substrate) prior to such pre-treatment
  • Figure 11B is a photomicrograph of the tungsten carbide substrate of Figure HA after pre-treatment.
  • the surface of the substrate is replete with grinding marks and impurities.
  • the surface of the substrate is cleared of grinding marks and impurities, and tungsten carbide grains are exposed amid valleys of cobalt (compare Figure 6B) .
  • the pre-treatment process of the present invention involves use of the excimer laser only, and ablated cobalt is suitably removed by the nitrogen shielding gas, which is suitably introduced through the nozzle (550) , but which may be introduced across the surface of the substrate by another, simplistic nozzle (not shown) .
  • Figure 10A is a process timing diagram illustrating the orchestration of the lasers and the secondary and shielding gases in a complete surface treatment process including a pre ⁇ treatment and a coating fabrication regime.
  • FIG. 10A is a diagram illustrating the time at which each of these components is turned on and turned off.
  • the numbers on the timing diagram represent seconds.
  • the surface treatment system of the present invention is suitably employed to perform pre-treatment of the substrate.
  • Figure 10 illustrates a pre-treatment regime lasting approximately twenty seconds, in a time interval between "p0" and "pi", wherein the substrate is pre-treated by the excimer laser (e.g., 712) only, to prepare the surface of the substrate for further treatment.
  • the excimer laser e.g., 712
  • the nitrogen (shielding) gas is also turned on to convey ablated material (cobalt, oxides) away from the substrate.
  • the nitrogen is left on for a brief interval (from “pi” to "p2") after the excimer laser is turned off to ensure that the ablated material is completely removed from the surface of the substrate.
  • the surface treatment technique may be performed, combining pre-treatment and coating fabrication, as illustrated by Figure 10A. Therein, at a time “tO" the surface treatment commences. During the entire surface treatment process, extending from time “to” to time “t5", the excimer laser (e.g., 712), the secondary source (e.g., 720) and the shielding gas (e.g., 724) are turned on.
  • the excimer laser e.g., 712
  • the secondary source e.g., 720
  • the shielding gas e.g., 724
  • the excimer laser is operated during the entire surface treatment process ("to” through “t5") , generally according to the parameters set forth above. However, the output of the excimer laser may be modified "on the fly” during the coating regime, notably to initiate pre-treatment (in the interval between "to” and “tl”) , and to take up “slack” from the Nd:YAG laser which may be turned off at time “t3" (discussed hereinbelow) .
  • the excimer laser is suitably operated at 450 mJ at a pulse frequency of 280 Hz. As illustrated by Figure 10A, it is not necessary to turn the Nd:YAG laser (e.g., 714) on immediately at "to".
  • the excimer laser plays a principal role in surface ablation and breaking chemical bonds in the secondary source (e.g., C0 2 ) , and has the following beam delivery parameters: a. wavelength 192nm, 248 nm or 308 nm (nanometers) , in the ultraviolet range of wavelengths, preferably 248 nm; b. power output up to 200 W (watts) , preferably 100 W (A lower power, such as 75 W can be employed for round tools) ; c. pulse energy up to 500 mJ (millijoules) , preferably 450 mJ; d. pulse sequence frequency (repetition rate) up to 300 Hz (Hertz), preferably 280 Hz; e.
  • the secondary source e.g., C0 2
  • beam delivery parameters a. wavelength 192nm, 248 nm or 308 nm (nanometers) , in the ultraviolet range of wavelengths, preferably 248 nm; b. power output up to 200 W
  • the beam delivery system (BDS) for the excimer laser includes a rectangular lens to deliver a rectangular beam
  • the lens (focused) having dimensions 1 mm x % inch, and the lens is disposed about 18 inches upstream (towards the laser) from the nozzle aligned with the nozzle axis.
  • the excimer laser is on for 20 seconds at 350-380 mJ, pulsed at a frequency of 220-250 Hz, at 100 watts, and performs surface ablation
  • the excimer is on for 45 seconds at 450 mJ, pulsed at a frequency of 280 Hz, at 100 watts, and (i) reacts and breaks bonds in the secondary source
  • the Nd:YAG laser which plays a principal role in the diffusion function suitably has the following beam delivery parameters: a. wavelength 1.06 microns (E-6 seconds), in the infrared range of wavelengths; b. power output up to 1500 Watts (W) , preferably 1000 W; c. pulse energy up to 150 Joules (J) , preferably 50 J; d. pulse sequence frequency, continuous wave (CW) , burst mode, or Q-switch up to 1000 Hz (Hertz), preferably 120 Hz; e. pulse length (duration) up to 20 ms (milliseconds) , preferably l ms; f. beam profile - round; and g. divergence 55 mrad.
  • beam delivery parameters a. wavelength 1.06 microns (E-6 seconds), in the infrared range of wavelengths; b. power output up to 1500 Watts (W) , preferably 1000 W; c. pulse energy up to 150 Joules (J) , preferably
  • the beam delivery system (BDS) for the Nd:YAG laser includes a circular lens to deliver a circular beam (diffused) having a radius of inch, and the lens is disposed about 18 inches upstream (towards the laser) from the nozzle at an angle of approximately -30° (30° in a one direction) from the nozzle axis.
  • the Nd:YAG laser is not operated.
  • the C0 2 laser which plays a principal role in the supporting thermal balance, suitably has the following beam delivery parameters: a. wavelength 10.6 microns, in the infrared range of wavelengths; b. power output on the order of 500 - 10,000 Watts (W) , preferably 2000 W. c. pulse sequence frequency up to 25 Hz, pulse up to 25 microseconds; super-pulse frequency up to 20 KHz (KiloHertz) , and a super-pulse width up to 500 microseconds; d. energy density up to 0.32 J/cm 2 ; e. beam profile - round; f. divergence - 1% mm/m; and g.
  • the C0 2 laser is turned on approximately 12 seconds (“t2") after the excimer laser is turned on, for a duration of 28 seconds, pulsed at a super-pulse frequency of 1.5 kHz, at 2000 watts, to (i) maintain thermal balance during the process (synergy between the surface reaction and the gas reaction) (ii) change of absorption rate changes during the process (iii) control the substrate temperature at the order of 1 ns (nanosecond) .
  • the C0 2 laser may be turned off shortly prior to the end of the process (e.g., at time "t4") .
  • the pulsations of the excimer and Nd:YAG lasers work together to "hammer” (create a shock wave, stress, and relax) the at the components of the plasma, dissociating same, inter alia.
  • the phase relationship between the pulses delivered by these two lasers are preferably adjusted (coordinated) to optimize the concerted hammering, depending upon the particular application of the system. These parameters are, at best, empirically determined.
  • tubular substrates having exceptional depth e.g. , high L:D
  • a simple (e.g., flat) reflecting mirror within the ID of the tubular substrate to direct the incident energy beam to selected areas on the ID of the tubular substrate.
  • selected areas axial, circumferential, helical
  • the treatment can be varied from selected area to selected area, in a manner similar to that of Figures 13E, 13F and 13H) .
  • the present invention is useful for coating any of a number of substrates, several of which have been discussed hereinabove.
  • the inner or outer diameters of a helical travelling wave tube could be treated and/or coated, as well as to produce windows for traveling wave tubes.
  • Resistive heating elements could be treated and/or coated, for example, to aid in heat distribution, as well as the inner and/or outer surfaces of cookware.
  • Coatings can be fabricated on replacement hip joints, and the like, so that a portion of the object being coated is provided with a low-friction coating (with, if required, enhanced high load-carrying capacity) , while another portion of the object is provided with a porous or textured coating (e.g., to promote bonding to a bone surface).
  • Figure 15B shows a component 1562 of a ball bearing, which has had the entire surface of the component 1562 treated to have hard (e.g., diamond or DLC) coating 1566.
  • the coating 1566 will function as a heat sink, so as to remove heat from the ball and race, and for protecting against corrosion.
  • Figure 16B shows an alternate embodiment 1620 of a technique for fabricating a coating on a round tool.
  • an exemplary end mill 1622 (similar to the end mill 1602) is disposed on its side, with the nozzle and lasers coming from above (not shown) .
  • a plasma 1630 is formed at the tip of the end mill, and is walked along the length of the fluted portion in a manner similar to what has been described above (with respect to causing relative motion of a selected area on a larger substrate) .
  • the end mill should be rotated in concert with walking the plasma along the fluted portion, to ensure uniform coverage (coating fabrication) along the length of the fluted portion.
  • the techniques of the present invention are advantageous for fabricating a number of coatings for any number of purposes, for example corrosion-resistant and erosion-resistant coatings, and coatings that are inert with respect to a hostile operating environment (e.g., steam boilers and the like).
  • An advantage of the present invention is that entire surfaces of a substrate can be treated without heating the entire substrate. Prior art techniques which involve such "gross" heating of the substrate can cause, for example, an underlying steel substrate to lose its temper (hardness) when a diamond coating is applied (e.g., by a CVD process, or the like) .
  • refractory coatings can be fabricated on large surface areas, because the technique of the present invention can be performed in a continuous manner, in an ambient environment.
  • the advantages of the present invention include:
  • the parts can be manipulated, various layer thicknesses can be achieved, and the coating can be applied to specific areas of the part without masking.
  • the coating e.g., diamond
  • the coating will adhere well to substrates having more than 10% cobalt content, thereby substantially eliminating the need for specialty substrates.
  • the technique of the present invention can also be heteroepitaxial.
  • Substrates having complex geometries can be treated, and various dopants (e.g., boron) can be introduced into the surface treatment.
  • various dopants e.g., boron
  • the present invention is applicable to treating any of a number of substrates, including metal and non-metal substrates (non-metal substrates include ceramics and polymeric substrates) .
  • substrates including metal and non-metal substrates (non-metal substrates include ceramics and polymeric substrates) .
  • specific materials that can be treated, or introduced into the reaction system include, but are not limited to:
  • metals B, Al, Ti, Nb, Ta, Cr, Mo, W, Re, Hf, etc.
  • nitrides BN, TiN, TaN, Si 3 N 4 , etc.
  • boron and borides B, TaB 2 , TiB 2 , WB, FeB, NiB, etc.
  • organic compounds PTFE, Kevlar, Polyimides, Liquid Crystalline Polymers, Polyethyltetrathalate
  • an advantage of the techniques of the present invention is that there is no post-process finishing required to obtain a desired surface texture.
  • the ultraviolet laser itself (for example) can be used to ablate the surface to obtain virtually any texture ranging from rough to optically-smooth, simply by controlling its output and duration.
  • there is no need to seed the substrate (for subsequent growth of a coating) and there is an unprecedented ability to control crystal orientation.
  • both pre-treatment and post- finishing can be performed in-situ (as part of the overall process) .
  • post-finishing steps would be required to obtain a texture smoother than the texture achieved by deposition.
  • the resulting substrate (product- by-process) will not exhibit such scratches and will have a non- directional surface finish.
  • additional orifices 1736 are provided in the nozzle (jet) body to create a helical flow of an additional gas, such as an inert gas.
  • additional gas such as an inert gas
  • Figure 17B-17C (corresponding to Figures 12a-b of the parent case) show an embodiment of a nozzle for delivering gases e.g., as secondary elements), according to the present invention.
  • the nozzle 1750 is generally cylindrical, having a top opening 1752, a bottom opening 1754, and a central cavity 1756 within the body 1758 of the nozzle 1750.
  • the laser energy e.g., three beams LI, L2, L3
  • the substrate would be disposed below the nozzle.
  • the nozzle 1750 has two gas inlets: a first inlet 1760 for receiving a supply of gas containing a carbonaceous secondary element (e.g., CO, C0 2 , etc.), and a second inlet 1770 for receiving a supply of inert gas (as described hereinabove) .
  • a carbonaceous secondary element e.g., CO, C0 2 , etc.
  • the first gas inlet 1760 communicates with an outer channel 1212 disposed circumferentially (e.g., as a ring) around the body 1758 of the nozzle 1750.
  • a carbon-containing gas is introduced into the first gas inlet 1760 (under predetermined pressures) and flows around the body 1758 of the nozzle through the outer channel 1762.
  • a plurality of inner channels 1764 extend generally radially from the outer channel 1762 into the cavity 1756 of the nozzle, for introducing the carbon-containing gas into the cavity of the nozzle.
  • the inner channels 1764 are preferably downwardly-directed, towards the bottom opening 1754, in order to direct the carbon-containing gas toward the bottom opening 1754 of the nozzle 1750 and, subsequently, towards the substrate upon which a diamond or DLC coating is being fabricated.
  • the second gas inlet 1770 communicates with an outer channel 1772 disposed circumferentially (e.g., as a ring) around the body 1758 of the nozzle 1750.
  • An inert gas (as described hereinabove) is introduced into the second gas inlet 1770 (under predetermined pressures) and flows around the body 1758 of the nozzle through the outer channel 1772.
  • a plurality of inner channels 1774 extend generally radially from the outer channel 1772 into the cavity 1756 of the nozzle, for introducing the carbon-containing gas into the cavity of the nozzle.
  • the inner channels 1774 may be downwardly-directed, towards the bottom opening 1754, in order to direct the inert gas toward the bottom opening 1754 of the nozzle 1750 and, subsequently, towards the substrate upon which a diamond or DLC coating is being fabricated.
  • the outer channels 1762 and 1772 are analogous to a runner for a transfer mold, and the inner channels 1764 and 1774 are analogous to the gates of a transfer mold.
  • the inner channels 1775 (comparable to 1774) can be directed axially downwardly, through the body 1759 (comparable to 1758) , to exit at the bottom of the nozzle, as shown in Figure 17C.
  • an energy b eam 1 806 from an energy source 1808 is directed at the substrate.
  • the energy source 1808 can be located outside of the vacuum environment. To this end, it is illustrated that the energy beam 1806 would enter the vacuum environment (i.e. , enter the belljar) through a suitable window 1812.
  • the remaining components necessary for utilizing the invention as an adjunct to a CVD-like process are not necessary to show in Figure 18, as CVD processes, and the like, are well known.
  • Figure 19 shows an alternate embodiment of the present invention.
  • a target 1924 such as graphite
  • an energy source 1926 having energy beam 1928.
  • Energy source 1926 may be introduced from energy source 1902 by utilizing necessary optics and configuring sufficient parameters.
  • One of the lasers is an ultraviolet laser, such as an XeCl or KrF excimer laser. This is useful in the context of introducing a carbon-containing secondary element such as carbon monoxide (CO) .
  • a carbon-containing secondary element such as carbon monoxide (CO) .
  • CO carbon monoxide
  • an XeCl or KrF excimer laser single photon energies are in the order of bond dissociation of common carbon-containing molecules.
  • the bond dissociation energy of carbon monoxide is 1077 kJ/mol, a relatively strong (if not the strongest) bond among carbon- containing molecules.
  • the infrared (IR) lasers also contribute to the overall reaction.
  • the single photon energy levels of these lasers is just sufficient to move molecules to their vibrationally and rotationally excited states.
  • IR lasers are typically not powerful enough to break chemical bonds or knock off electrons from neutral molecules. Therefore, they normally cannot dissociate molecules by themselves unless they are used in conjunction with resonant multi-photon processes or in an induced chemical reaction.
  • a C0 2 laser is generally very powerful, and can supply high photon density which makes multiphoton processes viable. Such multiphoton processes are able to initiate further reactions and depositions.
  • a C0 2 laser can generate conditions analogous to high-pressure, high-temperature (HPHT) processes.
  • a nozzle is optionally used to introduce a secondary element into the reaction system, and the secondary element may be in gaseous form. Additionally, it was mentioned that a shielding gas can be used to contain the desired secondary element.
  • An inert (i.e, to the overall reaction which is occurring) gas may be used to deliver the secondary element.
  • the use of an inert gas will (a) prevent oxidation, (b) create an "envelope" for the secondary element, (c) direct the flow of a carbon-containing gas onto the substrate.
  • the inert gas may be selected from the group consisting of He, Ne, Ar, Kr, Xe, and N - the first three of these being the most cost-effective.
  • the gas delivered by the nozzle may also function as an "energy-transfer" gas (agent) , in which case the gas will be used to absorb energy for delivery to the carbonaceous species in the carbon-containing gas, which will contribute to breaking the bond in the carbon-containing gas.
  • the energy-transfer gas may advantageously be selected from the group consisting of He, Ne, AR, Kr, Xe, N, H, and SF 6 .
  • a carbon-containing gas may be introduced as a secondary element to the reaction system.
  • a secondary element include:
  • the laser is sufficient for breaking the ethylene bonds.
  • No other gas or agent e.g, SF 6 is required for transferring energy to break the carbon bonds.
  • a powerful C0 2 laser may be used (in combination with other lasers) .
  • the C0 2 laser can supply very high photon density which makes multiphoton processes viable. Such multiphoton processes are able to initiate further reactions and depositions, and can generate conditions akin to high-pressure, high-temperature processes.

Abstract

De l'énergie provenant par exemple d'un laser excimère UV (712), d'un laser Nd:YAG infrarouge (714) et d'un laser CO2 infrarouge (716) est dirigée à travers un ajutage (722) au niveau de la surface d'un substrat (702) pour mobiliser et vaporiser un constituant carboné (par exemple du carbure) au sein du substrat (par exemple de l'acier). Une source secondaire supplémentaire (par exemple un gaz contenant du carbone, tel que du CO2) (720) et un gaz de protection inerte (N2) sont également délivrés à travers l'ajutage. L'énergie fait réagir le constituant vaporisé et transforme sa structure physique (par exemple de carbone en diamant) en celle d'un matériau composite qui est diffusé en retour dans le substrat sous forme de matériau composite.
EP95927112A 1994-05-12 1995-05-11 Techniques de traitement de surface Ceased EP0752018A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US08/241,930 US5731046A (en) 1994-01-18 1994-05-12 Fabrication of diamond and diamond-like carbon coatings
US241930 1994-05-12
PCT/US1995/005941 WO1995031584A1 (fr) 1994-05-12 1995-05-11 Techniques de traitement de surface

Publications (2)

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EP0752018A1 true EP0752018A1 (fr) 1997-01-08
EP0752018A4 EP0752018A4 (fr) 1998-09-02

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JPH09320352A (ja) * 1996-05-24 1997-12-12 Nissin Electric Co Ltd 電線及びその製造方法
JP3555844B2 (ja) 1999-04-09 2004-08-18 三宅 正二郎 摺動部材およびその製造方法
US6969198B2 (en) 2002-11-06 2005-11-29 Nissan Motor Co., Ltd. Low-friction sliding mechanism
JP4863152B2 (ja) 2003-07-31 2012-01-25 日産自動車株式会社 歯車
US7771821B2 (en) 2003-08-21 2010-08-10 Nissan Motor Co., Ltd. Low-friction sliding member and low-friction sliding mechanism using same
US8814861B2 (en) 2005-05-12 2014-08-26 Innovatech, Llc Electrosurgical electrode and method of manufacturing same
GB201118698D0 (en) 2011-10-28 2011-12-14 Laser Fusion Technologies Ltd Deposition of coatings on subtrates
RU2494173C1 (ru) * 2012-01-23 2013-09-27 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Нижегородский государственный технический университет им. Р.Е. Алексеева" (НГТУ) Способ вакуумно-плазменного осаждения покрытия на режущую пластину из твердосплавного материала
US10612123B2 (en) 2015-02-04 2020-04-07 The University Of Akron Duplex surface treatment for titanium alloys
PE20190724A1 (es) 2016-05-17 2019-05-20 Commonwealth Steel Company Pty Ltd Proceso de tratamiento de superficies
RU2674795C1 (ru) * 2017-10-05 2018-12-13 Федеральное государственное бюджетное учреждение науки Институт физики металлов имени М.Н. Михеева Уральского отделения Российской академии наук (ИФМ УрО РАН) Многослойное износостойкое покрытие на стальной подложке

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AU3124295A (en) 1995-12-05
WO1995031584A1 (fr) 1995-11-23

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