WO1990002825A1 - Revetements en alliage metallique et procedes d'application - Google Patents

Revetements en alliage metallique et procedes d'application Download PDF

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Publication number
WO1990002825A1
WO1990002825A1 PCT/US1989/003774 US8903774W WO9002825A1 WO 1990002825 A1 WO1990002825 A1 WO 1990002825A1 US 8903774 W US8903774 W US 8903774W WO 9002825 A1 WO9002825 A1 WO 9002825A1
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WO
WIPO (PCT)
Prior art keywords
substrate
prealloyed
mole percent
alloy
stainless steels
Prior art date
Application number
PCT/US1989/003774
Other languages
English (en)
Inventor
M. Daniel Merz
Robert W. Knoll
Original Assignee
Battelle Memorial Institute
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 Battelle Memorial Institute filed Critical Battelle Memorial Institute
Publication of WO1990002825A1 publication Critical patent/WO1990002825A1/fr

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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
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • C23C4/08—Metallic material containing only metal elements

Definitions

  • This invention relates to protective metal alloy coatings, and methods of applying or forming such coatings on substrates.
  • Corrosion-resistant coatings of amorphous alloys of stainless steel are presently available for the protection of substrates which are subject to corrosive attack by their environment. Most of these alloys are stabilized in the amorphous state by one or more of the metalloid elements such as B, C, Si and P.
  • the coating described in the U.S. Patent No. 4,496,635 is capable of remaining amorphous at temperature up to 400°C. It consists essentially of the formula M a Cr fa T , where "M” is at least one element selected from the group consisting of iron and nickel, "T” is at least one element selected from the group consisting of tantalum, titanium, zirconium, hafnium, niobium, molybdenum, and tungsten. Quantity "a” is 35-75 mole percent, "b” is 5-20 mole percent, “c” is 5-55 mole percent, and "b” plus “c” is equal to at least 25 mole percent.
  • U.S. Patent No. 4,786,468 describes a coating consisting essentially of an alloy of stainless steel and at least one tantalum or tungsten present in a range of from 60- 90 mole%.
  • Examples in these patents describe depositing of such glassy stainless steel coatings by sputter deposition in n small scale experiments (less than or equal to 0.1 area substrates).
  • Sputter deposition requires a high vacuum environment and typically achieves a low deposition rate. It may be prohibitively expensive to sputter deposit onto large surfaces or to a large number of parts where coating thicknesses need to be between 25-250 microns.
  • Plasma spraying of alloy coatings is also recognized as an application method in the prior art. Such processes generally require plasma spraying in a low pressure atmosphere (vacuum) or in the presence of an inert gas.
  • a low pressure atmosphere vacuum
  • inert gas for example, studies of plasma sprayed Ta, Nb, Ti, and C stress the need for an inert gas atmosphere or vacuum to obtain dense, high purity coatings. See for example, E. Lugscheider et al., "Vacuum Plasma Spraying of Tantalum and Niobium", j. Vac. Sci. Tech. A3 (1985) 2469-2473; H.D. Steffens et al.; "A Comparison of Low Pressure Arc and Low Pressure Plasma Sprayed Titanium Coatings", J. Vac. Sci.
  • This invention overcomes these and other problems associated with plasma spraying of coatings onto substrates.
  • a method of coating a substrate comprises plasma spraying of particular prealloyed feed powders onto a substrate in an oxygen containing atmosphere. Such method enables the creation of an adherent, corrosion resistant, substantially amorphous and substantially homogeneous metallic refractory alloy coating on the substrate in spite of such spraying in the presence of oxygen.
  • substantially amorphous identifies a substance having a microcrystalline domain size of less than or equal to about 2.5 nanometers.
  • the particular prealloyed feed powders comprise a significant amount of an alloy of stainless steel and at least one refractory element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum molybdenum, and tungsten. It has been discovered that by controlling the preparation of such prealloyed feed powders, plasma spraying in air is capable of producing such adherent, corrosion resistant, substantially amorphous and substantially homogeneous metallic refractory alloy coatings on substrates.
  • the prealloying is preferably sufficient to achieve intimate mixing of the alloy elements on an atomic scale to produce intermetallic chemical bonding of the stainless steel elements with the refractory metal or metals.
  • the intent is to produce a prealloyed powder wherein most all of the particles of the particular batch comprise the same alloy or compound. What is required is that the feed powder contain a significant amount of the prealloyed material to achieve a coating which is sufficiently amorphous to have an appreciable advantageous effect on corrosion resistance.
  • the refractory element is preferably present in the preal ' loyed powder in a concentration from 30-85 mole percent, and the stainless steel is preferably present in a concentration of from 70-15 mole percent. It is anticipated that ' any of the stainless steels, such as the 300 and 400 stainless steel series, can be used to produce the desired prealloyed feed powder.
  • the thermal expansion/ contraction properties of the applied coating will be designed to fairly well match those of the particular substrate. The thicker the applied coating, the greater the desirability of closely matching the respective expansion/ contraction properties.
  • any suitable substrate to which the coating will adhere can be used.
  • the substrate will have a metallic or metallized surface to which the coating is applied and bonded.
  • suitable substrate materials are copper and steel.
  • Specific example steels include stainless steels selected from the group consisting of low carbon stainless steels, high carbon stainless steels, low alloy stainless steels, high alloy stainless steels including 400 Series and tool steels, and 300 Series stainless steels, or mixtures thereof.
  • the substrate surface is preferably treated by bead or grit blasting to roughen the bonding surface and achieve a strongly adhered coating.
  • An intermediate metallic bonding layer such as nichrome could also be applied to the substrate, with the prealloyed feed powder being subsequently sprayed onto the intermediate layer.
  • the thickness of the applied coating will depend upon the geometry of the substrate and the environment in which the material will operate, as will readily be appreciated by the artisan.
  • a small quantity (0.5kg) of a substantially prealloyed Ta-stainless steel powder was produced for plasma spraying.
  • the prealloyed feed powder starting material consisted of five stacks, each weighing approximately 105 grams, of alternating tantalum and 304 stainless steel sheets. Each stack was 3.8 cm x 1.9 cm x 1.5 cm in size and contained approximately 76 weight percent tantalum and 24 weight percent stainless steel. (Approximately 50 mole percent tantalum and 50 mole percent stainless steel.)
  • the materials in the stack were alloyed by arc melting each stack on a water-cooled copper hearth in an argon atmosphere. The resulting ingots were remelted several times, and then turned over and remelted at least once.
  • the alloy ingot material was very brittle and could be easily fractured by impact. Each ingot was reduced to a powder in a Pitchford Pica Model 3800 blender-mill. The produced powders were repeatedly sieved and regound until all powder to be used for plasma spraying passed through a No. 170 mesh (90 micron) screen. X-ray diffraction analysis of the powder revealed an intimate mixture of NiTa and FeTa intermetallic compounds. Scanning electron micrographs showed the particles to be single phase indicating that the intermetallic phases were intimately mixed.
  • Substrates coated in air with the above prealloyed feed powder were compared with substrates coated in air with a feed powder that had an insignificant amount of pre-alloying.
  • Such control powder consisted of -150/+325 mesh material comprised of approximately 50 mole percent Ta and 50 mole percent 304 stainless steel (approximately 77 weight percent Ta-23 weight percent stainless steel) .
  • Scanning electron microscope analysis of such powder indicated that less than 10 weight percent of the material was alloyed.
  • Scanning electron micrographs revealed that each particle was primarily a conglomerate of tantalum and stainless steel particles.
  • X- ray diffractions also showed that the ..particles consisted mainly of stainless steel and elemental Ta, as opposed to an intermetallic alloy.
  • Coatings of such powders were plasma sprayed onto copper and mild carbon steel (ASTM-A569) plates 0.32 cm thick by 12.7 cm or 15.2 cm diameter.
  • the backside of the substrate was directly water-cooled to maintain the substrate near ambient room temperature during the spraying process.
  • Those substrates were fastened to an O-ring-sealed reservoir having circulating 15°C water.
  • Various surface preparation methods were used to test the effect of surface quality on coating adhesion. The initial substrate surface was that of as-rolled plate metal, and this surface was either bead blasted or grit blasted.
  • a plasma sprayed nichrome was first applied to the substrate before the tantalum-stainless steel coating. Table 1 below identifies the various substrate surface preparation methods, labelled A, B, C, and D, that were employed.
  • Plasma spraying was performed with a Plasmadyne, Inc. hand-held spray gun under ambient conditions in open air.
  • the spray parameters are listed in Table 2 below.
  • Powder feed gear setting 30; gear A Gun-to-substrate distance: approximately 3 inches
  • the substrates were positioned face-up on a horizontal surface with a coating applied by manually sweeping the plasma gun across the surface at a rate of approximately 5 cm/sec.
  • the plasma jet was oriented normal to the substrate surface with an approximately gun-to-surface distance of 7 to 7.6 cm.
  • a single pass was sufficient to deposit a layer of 50-75 microns (0.002-0.003 inches) thick.
  • a coating 150-200 microns (0.006-0.009 inches) thick on a 15 cm diameter substrate could be made with three passes in less than two minutes. After three passes, the uncooled substrates reached an average estimated maximum surface temperature of 300°C. The water-cooled substrates reached approximately 50°C.
  • the coatings were analyzed to determine the crystalline phases present, surface topography and microstructure, chemical homogeneity, corrosion resistance, and adherence to the particular substrate. Crystallinity was measured by X-ray diffraction using Cu K alpha X-rays and a diffractometer, over the two-theta range of 10° to 80°. Surface structure and homogeneity were examined with a scanning electron microscope equipped with energy dispersive X-ray spectroscopy for elemental analysis. Corrosion rates were determined by soaking the coating in hot 8 molar HNO3 or 8 molar H 2 S0 4 at 100°C for seven days. Corrosion rates were determined by measuring the weight loss after- such soaking. Specimens were weighed before and after the hot acid soak and calculated using the following formula:
  • V (W x 24 x 365 x 10) / (S x G x H)
  • V corrosion rate, mm/yr.
  • W corrosion weight loss
  • Table 3 below lists the various powder types and substrates used for the coatings.
  • Specimens SS-W-1 and SS- W-2 were made from heterogeneous (unalloyed) mixtures of tungsten and stainless steel powders. X-ray diffraction of coatings produced from these specimens showed that the coatings consisted of stainless steel and elemental tungsten particles with no significant alloying.
  • Substrate Preparation Method ID No. Powder Type See Table 1
  • SS-W-1 Powder mixture 70 wt. water cooled copper/A % W powder and 30 wt.% 18-8 stainless steel (SS) powder
  • Ta-SS-3 uncooled copper/A,B,C,D Ta-SS-4 uncooled steel/A,B,C,D Ta-SS-5
  • Ta-SS-6 uncooled steel/B Ta-SS-7 uncooled copper/B Table 4 below is a side-by-side comparison of two of the substrates of Table 3, one being coated with a substantially prealloyed feed powder and the other being coated with the only 10% prealloyed feed powder.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating By Spraying Or Casting (AREA)

Abstract

Un procédé de revêtement d'un substrat consiste à pulvériser au plasma une poudre d'alimentation de préalliage sur un substrat. La poudre d'alimentation de préalliage comprend une quantité importante d'un alliage d'acier inoxydable et d'au moins un élément réfractaire choisi dans le groupe composé de titane, zirconium, hafnium, niobium, tantale, molybdène, et tungstène. La pulvérisation au plasma de ladite poudre d'alimentation est exécutée dans une atmosphère contenant de l'oxygène, et forme sur le substrat un revêtement en alliage réfractaire métallique sensiblement homogène, adhérant et résistant à la corrosion.
PCT/US1989/003774 1988-09-06 1989-08-31 Revetements en alliage metallique et procedes d'application WO1990002825A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US241,080 1981-03-06
US24108088A 1988-09-06 1988-09-06

Publications (1)

Publication Number Publication Date
WO1990002825A1 true WO1990002825A1 (fr) 1990-03-22

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2305939A (en) * 1995-10-06 1997-04-23 Ford Motor Co Thermally depositing a composite coating based on iron oxide

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2457907A1 (fr) * 1979-05-29 1980-12-26 Howmet Turbine Components Composition de revetement pour la protection contre l'oxydation a haute temperature des super-alliages et composants en super-alliages ainsi revetus
JPS58126960A (ja) * 1982-11-29 1983-07-28 Res Inst Iron Steel Tohoku Univ 炭素系高耐食性非晶質鉄合金
JPS59100263A (ja) * 1982-11-29 1984-06-09 Teikoku Piston Ring Co Ltd 溶射ピストンリング
US4453976A (en) * 1982-08-25 1984-06-12 Alloy Metals, Inc. Corrosion resistant thermal spray alloy and coating method
US4496635A (en) * 1980-04-09 1985-01-29 The United States Of America As Represented By The United States Department Of Energy Amorphous metal alloy and composite
EP0266299A2 (fr) * 1986-10-30 1988-05-04 United Technologies Corporation Revêtement de barrière thermique

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2457907A1 (fr) * 1979-05-29 1980-12-26 Howmet Turbine Components Composition de revetement pour la protection contre l'oxydation a haute temperature des super-alliages et composants en super-alliages ainsi revetus
US4496635A (en) * 1980-04-09 1985-01-29 The United States Of America As Represented By The United States Department Of Energy Amorphous metal alloy and composite
US4453976A (en) * 1982-08-25 1984-06-12 Alloy Metals, Inc. Corrosion resistant thermal spray alloy and coating method
JPS58126960A (ja) * 1982-11-29 1983-07-28 Res Inst Iron Steel Tohoku Univ 炭素系高耐食性非晶質鉄合金
JPS59100263A (ja) * 1982-11-29 1984-06-09 Teikoku Piston Ring Co Ltd 溶射ピストンリング
EP0266299A2 (fr) * 1986-10-30 1988-05-04 United Technologies Corporation Revêtement de barrière thermique

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, Vol. 103, 1985, (Columbus, Ohio, US) A. SANDT: "Amorphous Powders - a Material for Sprayed Coatings?" see apge 223 Abstract No. 181686a & Metall (Berlin), 1985, 39(8), 734-6 *
PATENT ABSTRACTS OF JAPAN, Vol. 4, No. 73, (C-12)(555) 28 May 1980; & JP A 5538969 (Tokyo Shibaura Denki) 18 March 1980 *
PATENT ABSTRACTS OF JAPAN, Vol. 7, No. 235 (C-191), 19 October 1983; & JP A 58126960 (Touhoku Daigaku Kinzoku Zauriyou Kenkiyuu Shiyochiyou) 28 July 1983 *
PATENT ABSTRACTS OF JAPAN, Vol. 8, No. 218 (C-245)(1655), 4 October 1984; & JP A59100263 (Teikoku Piston Ring) 9 June 1984 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2305939A (en) * 1995-10-06 1997-04-23 Ford Motor Co Thermally depositing a composite coating based on iron oxide
GB2305939B (en) * 1995-10-06 1999-05-26 Ford Motor Co Thermally depositing a composite coating on a substrate

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