EP0505561A1 - Procede d'application a basse temperature de revetements metalliques a resistance elevee sur un substrat et article produit par le procede - Google Patents

Procede d'application a basse temperature de revetements metalliques a resistance elevee sur un substrat et article produit par le procede

Info

Publication number
EP0505561A1
EP0505561A1 EP92900032A EP92900032A EP0505561A1 EP 0505561 A1 EP0505561 A1 EP 0505561A1 EP 92900032 A EP92900032 A EP 92900032A EP 92900032 A EP92900032 A EP 92900032A EP 0505561 A1 EP0505561 A1 EP 0505561A1
Authority
EP
European Patent Office
Prior art keywords
metal
substrate
coating
temperature
range
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.)
Withdrawn
Application number
EP92900032A
Other languages
German (de)
English (en)
Other versions
EP0505561A4 (en
Inventor
Scott A. Ploger
Lloyd D. Watson
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.)
US Department of Energy
Original Assignee
US Department of Energy
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
Application filed by US Department of Energy filed Critical US Department of Energy
Publication of EP0505561A1 publication Critical patent/EP0505561A1/fr
Publication of EP0505561A4 publication Critical patent/EP0505561A4/en
Withdrawn legal-status Critical Current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
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
    • C23C4/123—Spraying molten metal

Definitions

  • the present invention relates to a method for spraying a thin, uniformly dense metal coating on a substrate and an article of manufacture produced thereby.
  • This invention relates to a low temperature spray coating process which has been developed at the Idaho National Engineering Laboratory (INEL) , the process is now referred to as the Controlled Aspiration Process (CAP) .
  • the CAP process is set forth in some detail in U.S. patent no. 4,919,853 issued to Alvarez and Watson, April 24, 1990, for Apparatus and Method For Spraying Liquid Materials, the disclosure of which is herein incorporated by reference.
  • the nozzle herein identified as a converging/diverging nozzle is the nozzle disclosed in the '853 patent.
  • the CAP process using the converging/diverging nozzle of the '853 patent can be manipulated provide a process or method of mechanically adhering thin dense metal coatings of uniform thickness on substrates. These coatings have superior mechanical properties to coatings applied by other processes and because of the CAP process parameters permit metal coatings to be deposited on substrates which thermally degrade at temperatures far below the melting point of the metal being deposited thereon.
  • the CAP process of spray forming metals aspirates a molten metal into the throat of a converging/diverging gas nozzle, where the liquid is nebulized into a directed spray of rapidly cooling droplets.
  • the gas flow usually an inert gas such as argon
  • the incident metal consolidates into a strong deposit with negligible porosity at the interface between the coating and the substrate surface. Rapid cooling occurs in flight by a variety of thermodynamic mechanisms including convection and radiation as well as by convection and conduction upon arrival at the substrate surface.
  • Rapid solidification of the nebulized metal droplets in the deposit produced by the CAP process enhances the metallurgical properties by limiting grain sizes, by preserving constituent homogeneity, by preventing impurities from segregating into inclusion defects and by freezing metastable metallurgical phases that would otherwise decompose during cooling to room temperature.
  • the homogeneous dispersion of impurities is particularly important since by preventing the segregation of impurities as inclusion defects, the structural integrity of the metal coating is improved.
  • the CAP coating capabilities provide precise control of the spray forming process and the coatings which result therefrom have better mechanical properties due to the low gas pressure used in the CAP process with a low droplet velocity having low momentum permitting the gas in the plume to deflect away from the dynamic deposition area. This results in less gas entrapment in the deposit, and thus less bulk porosity in the coating layer. Particularly, using pressures approximately 10 psi above atmospheric pressure or in the range of about 20-25 psi absolute, low droplet velocity results in gentle droplet impact conditions and complete consolidation at the substrate surface. Adherent coatings having tensile strengths greater than 3000 psi have been prepared using the CAP process.
  • the most important aspect of the CAP process for obtaining low interfacial porosity and improved adhesion strength is the spatial uniformity of the mass and thermal fluxes in the plume which promotes complete consolidation of the first droplets to impact the substrate, thereby preventing "chill zone" formation.
  • Another feature of the CAP process is that the mass and thermal fluxes of the plume produced from the converging/diverging nozzle are uniform across the plume and can be varied as can the gas to metal mass ratio without changing the droplet size in order to control the in-flight cooling rates.
  • coating adherence to the substrate is also a function of the substrate surface treatment, it is important that the surface be grit blasted, ball peened, or otherwise roughened, as well as cleaned or degreased. Near perfect interfacial interlinkage has been achieved between sprayed tin coatings on grit blasted steel coupons, as coatings having virtually no interfacial porosity have been deposited.
  • a metal spraying technique known as the Osprey Process is theoretically capable of depositing metal coatings but the Osprey Process deposits coatings having relatively high porosity at the substrate surface and also produces plumes in which neither the mass flux nor the thermal flux is uniform across the plume.
  • the low mass and thermal fluxes at the leading plume edge in the Osprey Process form an interfacial chill zone with up to 10% porosity which is aggravated by the high fraction of small, completely solidified droplets produced at an Osprey plume periphery.
  • the Osprey nebulizing gas is pressurized from 100-200 psi absolute to shear its thick liquid metal stream, compared to the 18 to 25 psi absolute used with the CAP process.
  • coatings may be flame sprayed by mixing oxygen and a reactive gas such as acetylene and igniting the gas mixture to inject the liquid solids by combustion.
  • flame temperatures are normally from 3000 * C to 5000"C.
  • the process suffers from adverse reactions that may occur when metal particles are introduced into such a high temperature atmosphere and byproducts of the combustion process which accumulate on the substrate surface and degrade adhesion of the metallic coatings thus formed. For these reasons, flame spraying has typically been confined to ceramic coatings, where the combustion byproducts are a minor concern.
  • Plasma spraying is accomplished by using two electrodes, one a pointed tip and the other an annular ring to form a circular opening between the two electrodes where the gases are ionized into a plasma.
  • Both metal and ceramic powders may be introduced via a secondary gas stream into the resistant heated plasma which can reach temperatures of 15,000"C.
  • Plasma sprayed metallic coatings are lower in porosity than flame sprayed layers and they are naturally free of combustion byproducts.
  • the CAP process provides coatings which are substantially different from thermal, that is flame-and plasma-sprayed coatings.
  • the choice of melt feedstock for sprayed-forming coatings is very flexible since the metal is nebulized directly from a molten reservoir.
  • thermal spraying the particles need considerable attention to size distribution which are rarely uniform even from the same commercial lot which results in a difficulty in tailoring compositions of an alloy by mixing metal powders before plasma injection. Because there is a wide size and shape distribution of injected particles in the thermal processes, the cooling rates as well as the droplet aspiration rates all vary.
  • thermal spraying unlike the CAP process, high plume temperatures preclude achieving the rapid solidification benefits of the CAP process and induce metallurgical coating-substrate bonding.
  • Another object is of the invention is to provide a method of applying a dense metal coating to a substrate comprising, providing a substrate to be coated having a clean and roughened surface, and directing a plume of nebulized metal droplets toward the substrate surface wherein the droplet size distribution is in the range of from about 5 microns to about 15 microns for a time sufficient to produce a coating having a thickness not less than about 3 mils and a density not less than about 98% of theoretical density.
  • Another object of the invention it to provide a method of applying a dense metal coating to substrate comprising, providing a substrate to be coated having a clean and roughened surface, directing a plume of nebulized metal droplets toward the substrate from a converging/diverging nozzle having a throat at which the nebulized metal is introduced and an exit from which the metal droplets leave entrained in a carrier gas, wherein the mass flux at any point in the plume at and after the nozzle exit is substantially the same to provide a coating of uniform thickness having a density not less than about 98% of theoretical density.
  • Yet a further object of the invention is to provide a method of applying a dense metal coating of uniform thickness to substrate comprising, providing a substrate to be coated having a clean and roughened surface, directing a plume of nebulized metal droplets toward the substrate from a converging/diverging nozzle having a throat at which nebulized metal is introduced and an exit from which the metal droplets leave entrained in a carrier gas, wherein the mass flux at any point in the plume after the nozzle exit is substantially the same to provide a coating of uniform thickness.
  • Still another object of the invention is to provide a substrate having a rapidly solidified metal coating layer mechanically adhered thereto wherein the metal coating is uniform throughout in density, the coating having a thickness greater than about 3 mils and a density not less than about 98% of theoretical density.
  • a final object of the invention is to provide an article of manufacture produced by the process of providing a substrate having a clean and roughened surface, forming a plume of nebulized metal in a carrier gas wherein the metal droplet size distribution is in the range of from about 5 to about 15 microns and directing the plume toward the substrate for a time sufficient to provide a metal coating having a thickness of not less than about 3 mils on the substrate.
  • preheating the substrate to temperatures in the range of from 100°C to about 225°C produced superior coatings in that adhesion strength of the metal coatings on the substrate surface which had previously been cleaned and roughened were improved over the coatings deposited on substrates which were not preheated, due to superior interfacial wetting and reduced differential thermal stress during cooling.
  • Quantitative results include measurements of bend deflections, adhesion strengths, porous areas in tin layers, and roughness on external coating surfaces.
  • the sequence of experiments is set forth below, all of which were conducted at Idaho Falls.
  • the coating remained 1 inch wide, but the 15.7-inch/minute speed lowered thickness to .012 inch.
  • the temperature of the steel sleeve was a constant 125°C.
  • the nozzle operating pressure- was held at 23.9 psia.
  • the overall intent was to reproduce the 150 RDL coating as a control experiment on the new base metal preparation pattern.
  • Operating pressure was also held at 22.9 psia for consistency with 178-1 VER.
  • the air gun heating element was turned on at maximum power and the nozzle temperature was raised from 400 ⁇ C to 500 ⁇ C for the first time.
  • the desired thin molten film was achieved once the base metal speed was increased from 2.4 to 16.1 inches/minute to eliminate ridging.
  • the thin (.009 inch) layer formed between 200° and 225'C.
  • these coatings were relatively wide from the 3 inch nozzle to sleeve separation. These conditions also apply to the 150 RDL coatings, but they tended to fracture at somewhat lower deflections for indefinite reasons.
  • Thickness was not an important factor in coating ductility on the superior samples, because 153 RDL deposits were typically .025 inch in thickness and 160-0 HOR samples were .012 inch in thickness.
  • the amount of surface roughening during base metal preparation also had no obvious influence on flexural strength; in both sets fine and coarse grit sizes yielded similar results. This likely reflects comparably good consolidation and adhesion.
  • Photomicrographs were taken of various prepared samples.
  • the area averaged porosity concentrations ⁇ ere generally between 0 and 1% in the overwhelming majority of cases, independent of the spraying conditions, base metal preparation, deposition temperatures and other process parameters.
  • Excellent consolidation of the incident tin droplets typically was accomplished over the entire test matrix, and porosity was virtually never interconnected.
  • Photomicrographs also confirmed that the isolated areas of relative high porosity generally occurred near external coating surfaces where complete consolidation was not expected as with formation of surface roughness. Even in these worse case locations, porosity was still very low near the steel interface, so corrosion resistance would not be jeopardized.
  • surface roughness of the coating it was found that the amount of heat directed toward the surface during the coating deposition affected the depth of the indentations. It was found that surface roughness can be controlled within reasonable limits according to heat deposition. For rapidly cooled coatings, at least .001 inch of material has to be ground away to produce a smooth surface. Little or no grinding is required for coatings deposited at higher temperatures. However, for certain applications, some roughness can be desirable, where lubricant retention or paint adherence are critical, for example. In such applications, the dimpled, faceted surface of the rapidly cooled coatings may be ideal.
  • the typically excellent mechanical interlinkage achieved strong adherence between the coating and the base metal without high temperature metallurgical bonding.
  • other metals such as lead, cadmium, zinc, aluminum, copper, iron, chromium, cobalt and nickel as well as various alloys thereof are applicable to the process. Since the droplets can be cooled rapidly in flight, such coatings can be placed onto heat-sensitive materials with little or no heat degradation, plus roughened plastics, cloth fibers and even paper with appropriate measures. Examination of the plumes produced in this process show that the mass flux at any point in the plume after the nozzle exit is substantially the same and it is this uniformity of mass flux in the plume which is an important feature of the invention and which helps to provide a coating of uniform thickness.
  • Thermal flux is determined by convective cooling requiring both different gas/metal temperatures and gas/metal velocities. There are four complementary cooling regimes in the low velocitv CAP process:
  • the process of the present invention produces a plume wherein the nebulized metal has a very narrow droplet size distribution.
  • This distribution is in the range of from about 5 microns to about 15 microns, and it is. this uniform size distribution of droplets along with the uniform mass flux and thermal flux of the plume which results in these very dense, highly uniform thickness, strongly adherent, small grain size coatings.
  • Another feature of the invention is that the rapidly solidified metal coatings produce a homogeneous dispersion of impurities throughout the coatings, thereby precluding the segregation of impurities into inclusion defects.
  • Coatings of the type hereinbefore described have good adhesion strength attributable solely to mechanical adhesion, whereas adherent plasma deposited coatings typically rely on metallurgical bonding.
  • the CAP deposited coatings rely purely on mechanical adhesion, and tin coatings have exceeded 2100 psi tensile strength with some coatings exceeding 3000 psi.
  • a novel spray- coating system which permits production of a well defined plume of nebulized metal to be coated wherein the droplet size distribution is in the range of from about 5 microns to about 15 microns.
  • the plume is directed toward the prepared substrate at a low velocity and by adjusting the upstream gas pressure, the nebulizer can be turned on and off and the metal spraying rate can be throttled in accordance with CAP or Control Aspiration Process.
  • Varying the mass ratio of transport gas to metal in the range of from about 0.5:1 to about 4:1 helps control the temperature of the coating at the substrate surface.
  • these coatings can be adhered to base materials which degrade at temperatures well below the melting point of the coating metal. Thermal degradation of substrates having melting points lower than the metal deposited thereon is possible because:
  • the thermal flux seen by the substrate is the average of the gas and metal temperatures. With a typical gas to metal mass ratio of 2:1, the average temperature tends to be dominated by the gas, with allowance for different heat capacities.
  • Metal droplets are partially solidified or undercooled (solidification takes time and can be slower than cooling, especially for very small droplets) at impact, with a volume fraction of about 1/4 to 1/3 liquid, so the average droplet temperature is typically below the metal melting point.
  • the melting point of Sn is about 235"C but the temperature at the substrate surface is about 50 * C to about 125 * C; the melting point of Al is about 670"C, but the temperature at the substrate surface would be about 300 ⁇ C to about 400*C; the melting point of Cu is about 1085 ⁇ C, but the temperature at the substrate surface would be about 500 ⁇ C to about 600'C; the melting point of stainless steel is about 1400"C but the temperature at the substrate surface would be about 800'C to about 900 * C; the melting point of Co is about 1495°C but the temperature at the substrate surface would be about 900"C to about 1000"C; the melting point of Cr is about 1857 ⁇ C but the temperature at the substrate surface would be about 1200°C to about 1300 ⁇ C; the melting point of Ni is about 1455"C but the temperature at the substrate surface would be about 850*C to about 950'C.

Abstract

Procédé d'application d'un revêtement métallique dense (99 % environ de densité théorique) sur un substrat, au moyen d'une buse convergente/divergente pour nébuliser le métal en colonne comportant une masse et des flux thermiques uniformes et une répartition de la dimension des gouttelettes métalliques située entre 5 et 15 microns environ. On peut déposer les revêtements sur des substrats qui se dégradent thermiquement à des températures très inférieures au point de fusion des métaux déposés. L'invention décrit également des articles pourvus d'un revêtement et possédant des caractéristiques de liaison mécanique importantes.
EP19920900032 1990-10-18 1991-10-15 A low temperature process of applying high strength metal coatings to a substrate and article produced thereby Withdrawn EP0505561A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US59977390A 1990-10-18 1990-10-18
US599773 1996-02-12

Publications (2)

Publication Number Publication Date
EP0505561A1 true EP0505561A1 (fr) 1992-09-30
EP0505561A4 EP0505561A4 (en) 1994-05-18

Family

ID=24401030

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920900032 Withdrawn EP0505561A4 (en) 1990-10-18 1991-10-15 A low temperature process of applying high strength metal coatings to a substrate and article produced thereby

Country Status (4)

Country Link
EP (1) EP0505561A4 (fr)
JP (1) JPH05503249A (fr)
CA (1) CA2071492A1 (fr)
WO (1) WO1992006797A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2271733B (en) * 1992-10-20 1996-07-03 British Steel Plc Improvements to the continuous spray forming of metal strip
DE19630954A1 (de) * 1996-07-31 1998-02-05 Linde Ag Verfahren und Vorrichtung zur Herstellung von Überzügen auf biologischen und/oder chemischen Produkten, insbesondere Lebensmitteln, Tiernahrung, Pharmazeutika oder biotechnologischen Erzeugnissen
JP4520626B2 (ja) * 2000-11-27 2010-08-11 池袋琺瑯工業株式会社 グラスライニングの施工方法
CN101098759A (zh) * 2005-01-07 2008-01-02 株式会社神户制钢所 喷镀喷嘴装置以及喷镀装置
DE102015201927A1 (de) * 2015-02-04 2016-08-04 Siemens Aktiengesellschaft Verfahren zum Kaltgasspritzen mit Maske

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2282315A1 (fr) * 1974-08-21 1976-03-19 Osprey Metals Ltd Procede et appareil pour fabriquer des ebauches de metal par pulverisation
GB1574711A (en) * 1976-01-19 1980-09-10 Boc Ltd Production of metal castings
EP0181087A1 (fr) * 1984-10-03 1986-05-14 Westinghouse Electric Corporation Aubes de turbine pour turbines à combustion
GB2172827A (en) * 1985-03-25 1986-10-01 Osprey Metals Ltd Producing a coherent spray deposited product from liquid metal or metal alloy
EP0223104A1 (fr) * 1985-10-29 1987-05-27 Deutsches Zentrum für Luft- und Raumfahrt e.V. Revêtement pour un substrat et son procédé de fabrication

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US2330202A (en) * 1939-12-07 1943-09-28 Joseph B Brennan Method of making electrodes
US3305397A (en) * 1963-03-27 1967-02-21 Union Carbide Corp Method of producing charged negative cadmium electrode by spraying with molten mixture of cadmium and a metal displaced by treatment with a cadminum salt and hydrofluoric acid bath
GB1431895A (en) * 1972-06-30 1976-04-14 Alcan Res & Dev Production of aluminium alloy products
FR2213350B1 (fr) * 1972-11-08 1975-04-11 Sfec
US4302483A (en) * 1979-09-04 1981-11-24 Texasgulf Inc. Metallizing of a corrodible metal with a protective metal
CH663219A5 (de) * 1984-01-31 1987-11-30 Castolin Sa Flammspritzwerkstoff.
US4619845A (en) * 1985-02-22 1986-10-28 The United States Of America As Represented By The Secretary Of The Navy Method for generating fine sprays of molten metal for spray coating and powder making

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2282315A1 (fr) * 1974-08-21 1976-03-19 Osprey Metals Ltd Procede et appareil pour fabriquer des ebauches de metal par pulverisation
GB1574711A (en) * 1976-01-19 1980-09-10 Boc Ltd Production of metal castings
EP0181087A1 (fr) * 1984-10-03 1986-05-14 Westinghouse Electric Corporation Aubes de turbine pour turbines à combustion
GB2172827A (en) * 1985-03-25 1986-10-01 Osprey Metals Ltd Producing a coherent spray deposited product from liquid metal or metal alloy
EP0223104A1 (fr) * 1985-10-29 1987-05-27 Deutsches Zentrum für Luft- und Raumfahrt e.V. Revêtement pour un substrat et son procédé de fabrication

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO9206797A1 *

Also Published As

Publication number Publication date
CA2071492A1 (fr) 1992-04-19
JPH05503249A (ja) 1993-06-03
WO1992006797A1 (fr) 1992-04-30
EP0505561A4 (en) 1994-05-18

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