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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/60—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using solids, e.g. powders, pastes
  • C23C8/62—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using solids, e.g. powders, pastes only one element being applied
  • C23C8/68—Boronising
  • C23C8/70—Boronising of ferrous surfaces
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
  • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
  • C22C29/067—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds comprising a particular metallic binder
• • 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
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
  • C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates
• • 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
  • 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.]

Definitions

• a surface-hardened cemented carbide shape consisting essentially of primary grains of a refractory metal carbide distributed through a metal matrix, the metal matrix adjacent the surface between the carbide grains having a boridized layer characterized metallographically by the presence of an iron-group metal boride.
• refractory carbide hard metals comprising in large part of carbides of titanium, tungsten, and/or other refractory carbides cemented together by liquid phase sintering in the-matrix metal, the favorable properties are due in large part to the rather high intrinsic hardness of the carbides combined with the strengthening effects of the bonding metal.
• primary carbide grains is meant the grains or particles of the refractory carbide added directly to the composition during the formation thereof, and which still retain substantially their identity in the final composition as compared to secondary carbide grains which form by reaction during heat treatment.
• a machinable refractory carbide body comprising primary titanium carbide grains dispersed through a heat-treatable steel matrix which utilizes the intrinsic hardening effect of the primary carbide combined with the hardenability of the steel matrix.
• the machinable carbide body has one advantage over conventional cemented carbides in that the matrix of a composition containing about 50% by volume TiC and the balance substantially steel can be softened by annealing so as to lower the gross hardness of the composition to say 40 R such that the body can be machined to a desired shape and then hardened to upwards of 72 R by quenching the alloy from an elevated temperature similarly as is done in certain of the alloy tool steels.
• refractory carbide powder such as titanium carbide
• finely divided steel-forming ingredients is mixed with finely divided steel-forming ingredients followed by compacting the mixture into the desired shape in a mold, and then subjecting the resulting compact to liquid phase sintering by heating it to a temperature above the lowest melting phase of the matrix metal but below the melting point of the refrac- 3,811,961 Patented May 21, 1974 tory carbide.
• liquid phase sintering advantageous for our purposes in that dense products substantially free from porosity are obtainable.
• the fore-going type of composite metal has found use in a wide variety of applications such as forming dies, die nibs, wear resisting parts, size gages, machine parts, and the like.
• the soft matrix metal is preferentially worn away from around the carbide grains. While the primary carbide grains themselves provide resistance to wearing, they only do so provided they are securely embedded and anchored in the matrix metal. However, as the matrix metal is selectively worn or eroded away from around the grains, the grains tend to loosen and fall out. Such preferential wearing has its disadvantages in that it may result in a surface notch effect which lowers the resistance of the metal to impact. Thus, it would be desirable where the matrix is concern to provide high retained hardness at the surface of the machine part to avoid the aforementioned difiiculties.
• a heat treatable composition for example, a composition comprising about 50% by volume of TiC and the balance 50% by volume of a low chromium low molybdenum steel
• the hardened surface should be one having as low a. coeflicient of friction as possible, while providing optimum hardness in addition to anchoring the primary grains of refractory metal carbides.
• the surface hardening process should be one capable of hardening not only a steel surface but other alloys of the iron-group matrix metals, such as nickelbase and cobalt-base matrix metals.
• Another object is to provide a steel-bonded carbide in which the surface of the matrix surrounding the carbide grains is boridized to improve its resistance to erosion,
• the invention provides a surface hardened cemented refractory metal carbide article of manufacture consisting essentially of about 20% to 80% by volume of primary grains of a hard refractory metal carbide distributed through a metal matrix comprised substantially of an iron-group metal, e.g. a matrix alloy based on at least one iron-group metal, the surfacehardened cemented carbide being characterized by a microstructure adjacent the surface thereof consisting essentially of primary grains of said refractory metal carbide dispersed through a boridized layer of said metal matrix, the boridized layer being comprised of an irongroup metal boride, such as iron boride, cobalt boride and nickel boride.
• an irongroup metal boride such as iron boride, cobalt boride and nickel boride.
• the primary grains of refractory metal carbides include those selected from the group consisting of carbides of chromium, tungsten, molybdenum, titanium, zirconium, hafnium, niobium, tantalum and vanadium. While the amount of carbide in the composition may range from about 20% to 80% by volume, a range of about 30%.
• a preferred steel matrix composition for boridizing is one containing by weight about 1% to 6% Cr, about 0.3% to 6% M0, about 0.3% to 0.8% C and the balance substantially iron.
• Another preferred steel matrix composition for boridizing is one containing by weight about 6 or 7% to 12% Cr, about 0.6 to 1.2% C, about 0.5% to 5% Mo, up to about 5% W, up to about 2% V, up to about 3% Ni, up to about 5% cobalt and the balance substantially iron.
• a further steel matrix composition is a low carbon heat treatable composition containing by weight about to 30% Ni, 0.2% to 9% Ti, and up to 5% Al, the sum of the Ti and Al not exceeding about 9%, up to about 25% Co, up to about 10% Mo, and substantially the balance of the matrix at least about 50% iron; the metals making up the matrix composition being proportioned such that when the nickel content ranges from about 10% to 22% and the sum of the Al and Ti is less than 1.5% and the Co and Mo contents are each at least about 2%; and such that when the Ni content ranges from about 18% to 30% and the Mo content is less than 2%, the sum of the Al and Ti exceeds 1.5%.
• This matrix alloy forms soft martensite when quenched from a solution temperature of about 1400 F. to 2150 F. (760 C. to 1165 C.) and age hardens when heated at a temperature of about 500 F. to 1200 F. (260 C. to 650 C.) for about three hours.
• Examples of other matrix metals other than steel are the iron-group metals nickel, cobalt and nickel-base and cobalt-base alloys. These metals can be boridized to form nickel boride and cobalt boride.
• cemented carbides mentioned hereinabove are produced by powder metallurgy.
• a composition comprising primary grains of titanium carbide dispersed through a low chromium, low molybdenum steel composition, such a composition comprising 40% by weight of TiC and 60% by weight of steel may be produced as follows:
• a l000-gram charge of TiC powder of about 5 to 7 microns in size is mixed with a 1500-gram charge of a steel-forming mixture calculated to form a matrix steel containing about 1.25% Cr, 2.5% M0, 0.4% C and the balance carbonyl iron powder of about 20 microns in size.
• the powdered ingredients have mixed therewith 1 gram of parafiin wax for each 100 grams of ingredients. The mixing is carried out in a steel mill for about 40 hours with the mill half full with steel balls, using hexane as the vehicle.
• the mixture is removed and vacuum dried.
• a proportion of the mixed product is compressed in a die at 15 tons/sq. in. to form a die nib of the desired size.
• the die nib is then liquid phase sintered at a temperature of about 1435 C. (about 2615 F.) for about one-half hour at a vacuum corresponding to about 20 microns of mercury or better.
• the assembly is cooled and then annealed by heating to 900 C. (about 1565 F.) for 2 hours followed by cooling at a rate of about 15 C./
• the die nib is finished machined to the desired size.
• the nib is then cleaned up and boridized. After the nib has been boridized, it is then hardened by austenitizing at 1750 -F., followed by quenching in an oil bath.
• a pack cementation process is used.
• a stainless steel retort is used in which the cover is sealed to the retort flange, the retort cover and the flange being machined to a smooth finish before each run to assure a gas-tight seal.
• a new nickel-plate A151 321 stainless steel O-ring is placed between the retort flange and the cover for each run.
• a typical powder pack is a mixture by weight of about 5% boron and about 95% aluminum oxide, the mixture containing 0.75% by weight of a halide energizer (e.g. ammonium bifluoride and potassium fluoride).
• a halide energizer e.g. ammonium bifluoride and potassium fluoride.
• the boron powder used is amorphous, has a particle size of about 5 microns and is about 90% to 92% pure.
• the main impurities are 6.2% Mg, 0.1% Fe and 2.2% O.
• aluminum oxide had a particle size of about 325 mesh.
• the pack may contain by weight from about 1% to 50% boron, a small but effective amount of a halide energizer (e.g. up to about 2%) and the balance an inert diluent such as alumina. Examples of the inert metals.
• the powders in appropriate quantities are mixed together and blended in a rotary blender containing stainless steel balls for 1 to 2 hours.
• the samples to be boridized are thoroughly degreased in trichloroethylene vapors and then honed with '400 mesh alumina grit. The honed samples are then packed in the retort containing the boridizing pack. The retort is filled densely with the powder pack so as to leave no empty space at the top and the cover then sealed to the retort flange as described hereinabove.
• the charged retort is heated in a furnace to 1550 F. (or the range of 1350 F. to 1700" F.) and held at temperature for about 10 to 35 hours, e.g. 24 hours. During this period, boron is deposited onto the surface of the sintered shape via boron halide vapors formed in the pack. The boron then diffuses into the surface and forms iron boride. At the end of the 24-hour period, the retort tive compositions as follows:
• the surface-hardened samples are either cleaned in the ultrasonic cleaner or by liquid honing to remove any powder sticking to them.
• compositions of the samples were-as follows:
• Matrix contains by weight 10% Cr, 3.0% M0,
• TiC 55 Matrix contains by Weight 18% Ni, 8.5% Co,
• TiC 45 Matrix contains by weight 18% Ni, 8.5% Co,
• TiC 55 Matrix contains by Wei ht 14% Or, 6% Ni, 5% Co, 1.5% Ti, bal. Fe.
• Matrix contains by weight 71% Ni,-18% Cr, 8%
• the samples were hardened according to theirrespec- No. 1 composition.Quenched from 1750 F., using a blast of inert gas, followed by tempering at 375 F. for 1 hour.
• the eutectic FeFe B tends to form which melts at about 2100 F. and therefore the hardening heat treatment should preferably be confined below this temperature to preserve the hard coating.
• the boride coating on the surface of each sample was identified by X-ray diffraction analysis and showed the presence of Fe B. and FeB. Approximately 1.5 to 2 mils thick coatings were obtained on all samples.
• the microhardness of the coating was measured by making Vickers :microhardness indentations using 25 g. load in the surface in the matrix region clear of any of the dispersed primary carbides. The hardness determinations are given in Table 2 as follows before and after boridizing:
• the substrate may be heat treated after .boridizing, it is advisable to employ a boridized layer of up to about 2. mils in thickness (0.002 inch) in order to minimize cracking of the boridized layer due to quenchmg.
• the boridized layer may range above 2 mils (0.002 inch) and up to about 7 mils (0.007
• a rod is. first produced by compacting a titanium carbide steel mixture comprising about 45% by volume of TiC and the balance (about 55% by volume) of a steel matrix having a composition consisting essentially of about 3% Cr, 3% Mo, 0.65% C and the balance iron.
• the compacted rod is liquid phase sintered in vacuum at a temperature of about 1435 C. (about 2615 F.) for about one-halfhour.
• the rod is furnace cooled to room temperature to provide an annealed hardness of about 47 R
• the annealed rod is finished machined to the desired diameter and the threads are: precision out along one length of the rod while the opposite length is knurled.
• the threaded gage is boridized as describedherein, the threads of which are thereafter cleaned and lapped to the final
• the boridized thread gage is used without any subsequent heat treatment to avoid volumetric size change and distortion normally caused by high temperature oil 'quench.
• the surface hardness' is generally infexcess of 1500VHN..
• Boridized drills and broaches are similarly produced from the titanium carbide steel compositions oftheaforementioned type. i
• an advantage of the boridized 'lay er' is that it confers low friction propertiesto the surface ofthe sintered refractory "carbidematerial, While at the same. time, conferring improved wear resistance to the metal. matrix surrounding the refractory carbide grains- Where the matrixisheattreatable, particularly a steel matrix, the coated sintered refractory carbide material can be hardened andtemperd by the usual heat treatment employed for the matrix in'the uncoated con- 'dition, provided sufficient care is takento avoidoxidizing or otherwise chemically changing the coating.
• the steelbonded carbide from a relatively high temperature, eg.
• inert 'gas such as argon
• compositions which may be boridized in accordance with the invention are as follows:
• the matrix metals employed in sintering and bonding the refractory carbide preferably contain at least 50% by weight of at least one of the iron group metals iron, nickel and cobalt, the refractory metal carbide ranging from about 20% to 80% by volume with the matrix metal making up substantially the balance.
• the invention is applicable to steel-bonded carbides and, in particular, to titanium carbide tool steel compositions comprising primary grains of refractory carbide, such as TiC, of about 20% to 80% by volume dispersed through the following steel matrices making up substantially the balance:
• the matrix comprising a high nickel alloy containing by weight about 10% to Ni, about 0.2 to 9% Ti, up to about 5% Al, the sum of Ti and Al content not exceeding about 9%, less than about 0.15% C, up to about 25% Co, up to about 10% Mo, substantially the balance of the matrix being at least about 50% iron, the metals making up the matrix composition being proportioned such that when the nickel content ranges fromabout 10% to 22% and the sum of Al and Ti is less than about 1.5 the molybdenum and cobalt contents are each at least about 2%, and such that when the nickel content ranges from about 18% to 30% and the molybdenum content is less than 2%, the sum of Al and Ti exceeds 1.5%.
• the foregoing matrix steels are characterized in the heat treated state by the presence of martensite.
• matrix steel (A) the refractory carbide tool steel produced therefrom is heat treated by heating it to above the austenitizing temperature, e.g. to 1750 F., and then quenching it to form hard martensite.
• the refractory carbide tool steel is boridized, it is preferred that the quenching be achieved by a blast of inert gas to avoid spalling of the boridized layer.
• the steel may be tempered by heating over the temperature range of about 250 F. and 550 F. for up to about 5 hours.
• the matrix is similarly heat treated by quenching from above the austenitizing temperature in the range of about 1700 to 2050" F., e.g. from 1750 F.
• the tempering is conducted at a higher temperature, e.g. from about 900 F. to 1050 R, such as 1000 F., for about 1 or 2 hours, wherein secondary hardening effects are obtained due to the formation of secondary carbides.
• refractory carbide steel com ositions produced therefrom by subjecting the steel to a solution treatment by cooling it (e.g. air cooling) from a solution temperature of about 1400 F. to 1950 F. (760 C. to 1100 C.) to produce a microstructure in the matrix characterized by the presence of soft martensite.
• the matrix surrounding the carbide grains is age-hardened by heating the refractory carbide steel at a temperature of about 500 F. to 1200 F. (260 C. to 650 C.) for about three hours.
• a typical agehardening temperature is 900 F. (483 C.).
• the matrix can be maintained in a relatively soft condition to provide toughness while providing a very hard surface by virtue of the lboridized layer.
• the boride coatings enable the production of refractory carbide articles such as molds, dies, sand blasting nozzles, rolls, etc. Such articles in use usually contact hard particulate matter which normally selectively wears away the matrix surrounding the primary carbide grains.
• One of the advantages of the steel matrix is that it can be annealed to enable the machining of sintered refractory carbide stock which can then be coated. The dimensional changes during boridizing are negligible as the coating is formed substantially by the inward diffusion of boron.
• Sand blasting nozzles were produced from an annealed titanium carbide tool steel and boridized in accordance with the invention.
• the composition comprised 45 vol. percent TiC and the balance a matrix steel containing 2.87% Cr, 2.87% Mo, 0.6 5% C and the remainder iron.
• the nozzles were heat treated to achieve a substrate hardness of 68 to 70 R The life of the nozzles was markedly improved. The rate of wear and erosion was substantially less than that experienced on nozzles made of ceramic, hardened tool steels, boron carbide and the aforementioned titanium carbide tool steel in the hardened but unboridized state.
• a surface-hardened cemented carbide article of manufacture consisting essentially of about 20% to by volume of primary grains of a hard refractory carbide selected from the group consisting of primary carbides of chromium, tungsten, molybdenum, titanium, zirconium, hafnium, niobium, tantalum and vanadium distributed through a steel matrix selected from the group consisting by weight of (A) about 1% to 6% Cr, about 0.3% to 6% Mo, about 0.3% to 0.8% C and the balance essentially iron; (B) about 6% to 12% Cr, about 0.5% to 5% Mo, about 0.6% to 1.2% C, up to about 5% W, up to about 2% V, up to about 3% Ni, up to about 5% Co and the balance essentially iron; and (C) a high nickel alloy steel containing about 10% to 30% Ni, about 0.2 to 9% Ti, up to about 5% Al, the sum of the Ti and Al content not exceeding about 9%, up to about 25 Co, up to about 10% Mo,

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Powder Metallurgy (AREA)
• Chemical Vapour Deposition (AREA)
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Cited By (16)

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• 1972
  • 1972-03-09 US US00233282A patent/US3811961A/en not_active Expired - Lifetime
  • 1972-05-04 DE DE19722221875 patent/DE2221875A1/de not_active Withdrawn
  • 1972-06-26 JP JP47063344A patent/JPS5210129B2/ja not_active Expired
• 1973
  • 1973-02-26 CA CA164,564A patent/CA973069A/en not_active Expired
  • 1973-02-26 GB GB944073A patent/GB1373750A/en not_active Expired
  • 1973-03-07 IT IT9364/73A patent/IT982068B/it active
  • 1973-03-08 FR FR7308257A patent/FR2175164A1/fr not_active Withdrawn

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