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
  • C23C12/00—Solid state diffusion of at least one non-metal element other than silicon and at least one metal element or silicon into metallic material surfaces
  • C23C12/02—Diffusion in one step
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B77/00—Component parts, details or accessories, not otherwise provided for
  • F02B77/02—Surface coverings of combustion-gas-swept parts
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/9335—Product by special process
  • Y10S428/938—Vapor deposition or gas diffusion
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/9335—Product by special process
  • Y10S428/941—Solid state alloying, e.g. diffusion, to disappearance of an original layer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12014—All metal or with adjacent metals having metal particles
  • Y10T428/12028—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
  • Y10T428/12063—Nonparticulate metal component
  • Y10T428/12139—Nonmetal particles in particulate component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
  • Y10T428/12812—Diverse refractory group metal-base components: alternative to or next to each other

Definitions

• these refractory metals may be required to Withstand high temperature heating in oxidizing atmospheres, under conditions tending to cause rapid or excessive oxidation of the metal unless it is surface protected.
• parts made of molybdenum or a molybdenum alloy typically molybdenum alloyed with around 0.5 percent titanium or zirconium
• such parts may be required to operate in air or other oxidizing atmosphere in temperatures in the range of 1800" F. to 3600 F. and over periods of exposure to such temperatures that tend to produce failures, though they may be small and of a pin hole order, in protective coatings heretofore devised.
• our general object is to provide these refractory metals with a surface diffused protective coating having such assured continuity, resistance to interruptions however small, and resistance to high temperatures over extended exposure in oxidizing atmospheres, as to insure the base metal against physical or chemical impairment.
• this object is accomplished by diffusing both silicon and boron into the base metal surface to depths corresponding to those achieved according to past techniques for diffusion of one metal into the surface of another, thereby to produce a protective coating in which the silicon, boron and base metal are interalloyed or combined, and the silicon and boron at the surface are alloyed in a state of continuously uniform distribution resulting in corresponding uniformity of the protection given the base metal.
• While the invention contemplates generally the diffusion of the silicon and boron either simultaneously or sequentially into the base metal surface, We preferably employ a procedure calculated to assure uniformity in the final diffused state of these metals, by obviating any tendency for one to diffuse difierentially to any consequential degree, by first combining the silicon and boron before their diffusion application to the base metal.
• our preferred procedure is to heat together the silicon and boron in a non-oxidizing atmosphere at temperatures that may correspond to those employed for the subsequent diffusion, thereby to alloy the silicon and boron or complex them into the nature of a silicon boride, so that the two metals will have become 3,090,702 Patented May 21, 1963 precombined in this sense and thereby caused to diffuse with greater assurance of uniformity, when subsequently heated against the base metal surface.
• Our preferred practice for diffusion purposes is to heat the base metal in what physically is a well known form of pack comprising a metal box containing the parts to be treated in surface contact with a powdered mixture containing the silicon and boron to be diffused.
• Such mixtures include an inert diluent whose primary function is that of a partitioning medium between the active particles (silicon-boron), and a halogen source which according to known diffusion practices serves as a chemical mechanism in the metal diffusion.
• the base metal may be of the group consisting of molybdenum, tantalum, tungsten and columbium, or any of these metals alloyed with small percentages of other metals such as titanium and zirconium, or with other of these same refractory metals.
• the base metal to be surface protected may have any of various physical forms such as nozzles, blades, vanes, shells or other configurations which in use undergo exposure to high temperatures, say in the range of about 1800 F. to 3600 F.
• the silicon source employed preferably is powdered elemental silicon in the range of 60 to 325 mesh, or other powdered silicon sources such as ferro-silicon, from which the silicon is releasible for alloying with the boron.
• the boron source preferably is amorphous boron at corresponding (60 to 325 mesh) fineness, although we may employ ferro boron, or boron in other form from which the elemental boron is available for alloying, as such, with the silicon.
• the halogen source to be used in the diffusion pack may be any one or more of the halogens or halogenreleasing compounds commonly used in diffusion techniques of this character. Such compounds are known to release halogen under the treatment conditions for combination with the metal being diffused and with the base metal itself.
• the conventionally employed halogens and halides include fluorine, chlorine, bromine, iodine, and the metal and ammonium salts of each. Without intending limitation, we may state a preference for the use of ammonium bifluoride in the present process, particularly as applied to the surface protection of a base metal which is essentially molybdenum.
• the diluent component of the powdered pack mixture may be any of various refractory materials in finely divided or powdered form, and having a mesh size from about 50 to 350 mesh. Clay, kaolin, zirconia, 'beryllia, and tabular alumina are illustrative.
• the latter may contain about 5 to 70% silicon (calculated as elemental silicon component of the pre-formed boron silicon alloy), about to 1 0% boron, similarly calculated as elemental boron, between about 0.1% to 1.0% halogen source, with the remainder inert diluent, in the range of about 25 to 75%, all percentages being by weight.
• the finely powdered boron, silicon, halogen source and diluent are uniformly admixed and heated in the absence of oxygen within the temperature range of about 1600 to 2200 F. over a period of time, say in the range of 8 to 12 hours, required to uniformly alloy or complex these metals (i.e. the silicon and boron).
• the resulting finely powdered silicon-boron alloy is then mixed uniformly with a new charge of halogen source of the same proportion to form the diffusion pack composition.
• the latter is packed in direct contact with the base metal in a retort box as described, and the latter, with its contents, is heated to a temperature in the 1600 F. to 2200 F. range over a period of about 8 to 12 hours.
• the boron and silicon are caused to diffuse into the base metal surface and to alloy or combine with the base metal, physically to a state such that the alloyed base metal, silicon and boron form a fully continuous protective coating, which I have found to be extraordinarily resistant to high temperature oxidation or physical rupture.
• Example I Three pieces of molybdenum alloy of the approximate composition 0.5% Ti, 0.07% Zr, balance molybdenum, were treated by diffusion into their surfaces of three separately prepared interdifiused boron-silicon compositions made by heating in a retort box at about 1800" F. for hours, a mixture of 34% silicon powder, 65% tabular alumina, ammonium bifluoride, and
• composition A 1% amorphous boron powder Composition B 3% amorphous boron powder Composition C 5% amorphous boron powder (These percentages being by Weight of the total mixtures.)
• the three molybdenum alloy samples were packed in separate treatment boxes respectively with the combined silicon-boron resulting from the compositions A, B and C, above (separated from the residual alumina and bifiuoride), together with fresh alumina and bifluoride in similar proportions, i.e. in each instance with about 65 alumina and ammonium bifluoride, the remainder silicon-boron.
• Example II A specimen of molybdenum alloy 0.5% Ti, balance molybdenum, was treated using composition A, above, and tested by heating with oxy-acetylene torch to 3000 F. in 25 seconds and holding temperature for 60 seconds. After 21 cycles of heating, there was no observed failure.
• Example 111 A specimen of molybdenum alloy 0.5% Ti, balance molybdenum, was treated. It was tested by heating in slowly moving air at 2700 F. The coating withstood 175 hours of testing without failure.
• a refractory base metal of the group consisting of molybdenum, tantalum, tungsten and columbium, and alloys of those respective metals that includes heating the base metal at a temperature between about 1600 F. and 2200 F. in a non-oxidizing atmosphere and in contact with a powdered mixture of an inert solid diluent, a halogen source and both boron and silicon distributed in said mixture in condition from which the boron and silicon are diffusible into the base metal, and thereby diffusing silicon and boron into the surface of the base metal to form a continuous protective coating integrated therewith.
• said powdered mixture contains between about 5% to 70% silicon calculated as elemental silicon, between about to 10% boron calculated as elemental boron, between about 0.1 to 1.0% halogen source, and between about 25% to of said inert diluent.
• a refractory base metal of the group consisting of molybdenum, tantalum, tungsten and columbium, and alloys of those respective metals that includes heating together powdered silicon and boron in a non-oxidizing atmosphere and distributed in a powdered mixture of an inert diluent and a halogen source at a temperature between about 1600 F. and 2200 F., then heating the base metal in a non-oxidizing atmosphere at a temperature between about 1600 F. and 2200 F. with a powdered mixture containing the silicon and boron resulting from said heating together with inert diluent and a halogen source, and thereby diffusing silicon and boron into the base metal to form a continuous protective coating integrated therewith.
• the last mentioned powdered mixture contains between about 5% to 70% silicon calculated as elemental silicon, between about /s% to 10% boron calculated as elemental boron, between about 0.1% to 1.0% halogen source, and between about 25 to 75% of said inert diluent.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Combustion & Propulsion (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Powder Metallurgy (AREA)
• Chemically Coating (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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Cited By (19)

Citations (7)

• 1961
  • 1961-01-23 US US83953A patent/US3090702A/en not_active Expired - Lifetime
• 1962
  • 1962-01-18 GB GB1824/62A patent/GB934542A/en not_active Expired
  • 1962-01-22 DE DE19621446118 patent/DE1446118B2/de active Pending

Patent Citations (7)

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