Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/1035—Liquid phase sintering
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/16—Metallic particles coated with a non-metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/17—Metallic particles coated with metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
  • B22F7/02—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers

Definitions

• a method of consolidating Tough-Coated Hard Powders (TCHP) to essentially full density at low or no pressure, and articles consolidated using this method, is disclosed.
• the method is a cost-effective method of making sintered bodies of TCHP materials based on liquid phase sintering that provides increased value over conventional hard articles and tool materials known presently in the art.
• Sintering may be defined as the thermal treatment of a powder or compact for the purpose of bonding the particles together to create a solid article.
• the powder is comprised of a mixture of powders of at least two distinct materials with different melting points, the powder mixture is compacted into a porous ("green”) body.
• LPS liquid phase sintering
• the rate of densification may be influenced by, for example, sintering temperature, sintering time, sintering pressure, sintering atmosphere, and weight fraction of the binder constituent present.
• Liquid phase sintering of conventional hardmetals such as tungsten carbide - cobalt (WC-Co) compacts is generally performed at sintering temperatures that range from 1325 0 C to 1475 0 C.
• WC-Co tungsten carbide - cobalt
• the cobalt will start to behave like a very viscous liquid at about 700 0 C and diffusion will increase with increasing temperature as Co viscosity correspondingly decreases.
• the grease-like behavior and viscosity of Co metal is believed to create capillary attractor forces resulting from the strong propensity of Co to wet as much WC surface as possible. This results in a rearrangement of WC particles and the composite begins to shrink even before the first liquid phase has formed.
• the Co binder metal begins to dissolve the WC particles and a ternary eutectic reaction begins to form a Co-W-C alloy.
• the increased surface wetting, liquefication, and capillary forces cause continued particle rearrangement and shrinkage of the powder mass into the shape of desired articles as grain boundaries move through the interface between the WC grains and Co binder phase.
• High density, uniformity, and WC stoichiometry in the sintered part are basic requirements for WC-Co microstructural integrity and strength. Ensuring proper local carbon balance during liquid phase sintering, which eliminates the formation of the brittle carbon-deficient C0 3 W 3 C eta phase and carbon porosity caused by too much carbon is also important in providing the fracture toughness of WC-Co materials. Eliminating strength-robbing porosity and grain growth in the microstructure can be accomplished through selection of an appropriate sintering temperature and pressure. For example, the temperature must be high enough to liquefy an adequate amount of material to accomplish the mass transfer necessary to fill the pores between particles while maintaining the temperature low enough to avoid WC overdissolution that causes grain growth.
• the invention provides a method of consolidating by liquid phase sintering a new class of designed-microstructure particulate materials with unprecedented combinations of property extremes called Tough-Coated Hard Powders (TCHPs, or EtemAloy ® ).
• This novel family of sintered particulate materials is comprised of one or more types of superhard Geldart Class C or larger ceramic or refractory alloy core particles having extreme wear resistance, lubricity, and other properties which are (1 ) individually coated with nanolayers of a metal compound having a relatively higher fracture toughness, such as WC or TaC, and (2) coated again with a second layer comprising a binder metal, such as Co or Ni.
• the combination of multiproperty alloys within the TCHP sintered structure allows the combination of normally conflicting performance extremes, including, but not limited to toughness, abrasiveness, chemical wear resistance, and light weight, at levels heretofore to provide materials with superior properties unavailable from the sintered homogeneous powders.
• TCHP materials are disclosed in U.S. Patent 6,372,346 to Toth, which is incorporated by reference herein. [019] The process of the present invention allows the integration of thermodynamically incompatible material phases and property extremes in a single material. Thus, TCHP materials can be engineered to combine hardness approaching that of diamond with fracture toughness greater than that of tungsten carbide, and weight approximately that of titanium. As a result, TCHPs can significantly exceed the wear resistance of conventional metal cutting and forming tools; abrasives; friction and wear products and thermal coatings; and automotive, aerospace, heavy industrial, and defense components.
• the method comprises providing a plurality of core particles comprised of one core particle material, or a plurality of different core particle materials chosen from metal and metalloid nitrides, metal and metalloid carbides, metal and metalloid carbonitrides, metal and metalloid borides, metal and metalloid oxides, metal and metalloid sulfides, metal and metalloid suicides, and diamond.
• An intermediate layer is provided on a majority of the core particles.
• the intermediate layer comprises a second compound, different in composition from the core particle material and having a higher relative fracture toughness.
• the second compound is capable of bonding with the core particle material and capable of bonding with a metal chosen from iron, cobalt, nickel, copper, titanium, aluminum, magnesium, lithium, beryllium, silver, gold, platinum and their mixtures.
• the combination of the core particle and the intermediate layer forms coated particles.
• An outer layer is applied to the coated particles.
• the outer layer comprises a metal chosen from iron, cobalt, nickel, and their mixtures and forms a substantially continuous outer layer on the intermediate layer.
• the combination of the coated particles and the outer layer forms component particles.
• a plurality of the component particles are shaped into an article.
• the article is sintered to substantially full density without significant external consolidation pressure at a temperature sufficient to liquefy at least a portion of the outer layer, and for a time sufficient to dissolve a portion of the intermediate layer in the liquid formed from the outer layer.
• Liquids formed from the outer layer and the intermediate layer are solidified prior to significant detrimental interaction of the liquids with the core particles.
• the core particle material has the formula M 3 X b , where M is a metal chosen from titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum, magnesium, copper, and silicon; X is an element chosen from nitrogen, carbon, boron, sulfur, and oxygen; and a and b are numbers greater than zero up to and including fourteen.
• the core particle material is selected from TiN, TiCN, TiC, TiB 2 , ZrC, ZrN, ZrB 2 , HfC, HfN, HfB 2 , TaB 2 , VC, VN, cBN, hBN, AI 2 O 3 , Si 3 N 4 , SiB 6 , SiAICB, B 4 C, B 2 O 3 , W 2 B 5 , WB 2 , WS 2 , AIN, AIMgB 14 , MoS 2 , MoSi 2 , Mo 2 B 5 , and MoB 2 .
• Metalloid elements are those elements located along the line between the metals and nonmetals in the periodic table.
• Metalloids generally include boron, silicon, germanium, arsenic, antimony, and tellurium. Polonium is often considered a metalloid, too.
• Non-limiting examples of nitride metalloids are cubic boron nitride (cBN) and Si 3 N 4 .
• An example of a carbide metalloid is B 4 C.
• An example of a bimetalloid compound is SiB 6 .
• Also disclosed herein is a method forming an article from particulate material that comprises providing a plurality of core particles comprised of one core particle material, or a plurality of different core particle materials, such as those selected from TiN, TiCN, TiC, TiB 2 , ZrC, ZrN, ZrB 2 , HfC, HfN, HfB 2 , TaB 2 , VC, VN, cBN, hBN, AI 2 O 3 , Si 3 N 4 , SiB 6 , SiAICB, B 4 C, B 2 O 3 , W 2 B 5 , WB 2 , WS 2 , AIN, AIMgB 14 , MoS 2 , MoSi 2 , Mo 2 B 5 , MoB 2 , and diamond; and [030] providing an intermediate layer on a majority of these core particles in an amount ranging from 10% to 80% by weight of the article.
• core particle material such as those selected from TiN, TiCN, TiC, TiB 2 , Zr
• the intermediate layer generally comprises a second compound, different in composition from the core particle material and has a higher relative fracture toughness, wherein the second compound is selected from WC, TaC, W 2 C, and a mixture of WC and W 2 C, thereby forming coated particles.
• the coated particles are typically treated as previously described, which includes applying an outer layer to the coated particles, the outer layer comprising a metal chosen from iron, cobalt, nickel, and their mixtures to form a substantially continuous outer layer on the intermediate layer, thereby forming component particles; [032] shaping a plurality of the component particles into an article; [033] sintering the article at a temperature sufficient to liquefy at least a portion of the outer layer, and for a time sufficient to dissolve from 5 to 90 volume % of the intermediate layer in the liquid formed from the outer layer to provide an effective amount of liquid to achieve substantially full density without significant external consolidation pressure, the solid portion of said intermediate layer preventing chemical interaction of the liquid with the core particles; and [034] solidifying liquids formed from the outer layer and the intermediate layer prior to significant detrimental interaction of the liquids with the core particles.
• the sintering temperature and time are such that they do not result in complete dissolution of the intermediate layer, but at most, lead to the dissolution of some part of the intermediate layer, such as 5-50% dissolution or 50-99% dissolution of the intermediate layer. Indeed, it is the solid portion of the intermediate layer that prevents chemical interaction of the liquid with said core particles.
• Fig. 1 is the pseudo-binary WC-Co phase diagram.
• Fig. 2 represents a typical TCHP sintered article.
• Fig. 3 is an SEM photograph showing that the TCHP structure is intact even when excessive Co is included.
• Fig. 4 is an SEM photograph showing effective prevention of WC layer dissolution during and after sintering.
• Fig. 5 represents a model of different TCHP materials at various sintering temperatures. This compares particle dissolution under various liquid phase sintering conditions.
• Fig. 6 is a table of calculated WC-Co solid and liquid phase compositions at various temperatures and cobalt contents.
• Fig. 7 are microstructural photographs of liquid phase sintered TCHP.
• the present disclosure describes methods of encapsulating and sintering fine particles having desired sets of properties with grain boundary modifiers having other properties, thus allowing for the design of previously impossible material-property combinations.
• the TCHP "building block" particle contains elements, such as hardness + wear resistance + toughness + binder metal + other designer properties, and gives the materials engineer thousands of new material grades with engineered properties simultaneously optimized at the nano-, micro-, macro- and functional levels.
• This merging of nanoencapsulation with the sintering of fine particles creates pseudoalloy structures integrating thermodynamically incompatible material phases and properties.
• the methods described herein comprise the formation of an article from particulate material.
• the particulate material, or TCHPs comprises a plurality of core particles, an intermediate coating on a majority of the particles, and an outer coating on the particles.
• the core particles can be a unique composite particulate material class that is comprised, for example, of one core particle material, or a plurality of different core particles materials chosen from metals or metalloids of nitrides, carbides, carbonitrides, borides, oxides, sulfides, and suicides, or diamond.
• the core particle materials is often a metal compound, having the formula M 3 Xb, where M is chosen from at least one element chosen from titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum, magnesium, copper, boron, and silicon, while X is chosen from at least one element chosen from nitrogen, carbon, boron, sulfur, silicon, and oxygen.
• M is chosen from at least one element chosen from titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum, magnesium, copper, boron, and silicon
• X is chosen from at least one element chosen from nitrogen, carbon, boron, sulfur, silicon, and oxygen.
• Non-limiting examples of such compounds include, TiN, TiCN, TiC, ZrC, ZrN, VC, VN, AI 2 O 3 , Si 3 N 4 , SiB 6 , SiAICB, W 2 B 5 , AIN, AIMgB 14 , MoS 2 , MoSi 2 , Mo 2 B 5 , and Mo 2 B.
• the plurality of core particles comprise at least one particle selected from diamond, cubic boron nitride, and hexagonal boron nitride, and their mixtures with each other or any of the above-described materials.
• X may comprise only one of nitrogen, carbon, boron, sulfur, silicon, and oxygen, or it may comprise a mixture of any or all of these components.
• a majority of the particles contain an intermediate layer comprising WC, W 2 C, tool steel, glassy and devitrified nanosteel alloys, silicon nitride, or tantalum carbide. Such materials have a fracture toughness greater than that of cubic boron nitride.
• the material of the intermediate layer only need to have a higher relative fracture toughness than that of the material comprising the core particles, as well as being capable of bonding with the metal compound(s) or materials forming the core particles and is also capable of bonding with a metal chosen from iron, cobalt, nickel, copper, titanium, aluminum, magnesium, lithium, beryllium, silver, gold, and platinum.
• the coated particles have an average particle size less than about 1000 microns. In another embodiment, the coated particles may have an average particle size of less than 100 microns, for example, less than about 50 microns, even less than 2 microns and, further, for example, of less than about 1 micron.
• the coated particles may have an average particle size in the range of 100-1000 nanometers.
• the intermediate layer may have a thickness, after sintering, in the range of from 5% to 50% of the diameter of the core particles. The thickness of the intermediate layer has an effect on the mechanical properties of the articles made therefrom.
• the coated particles when the coated particles (the core with an intermediate layer thereon) have an average particle diameter as measured graphically in a photomicrograph of a cross-section using the mean free path method of less than about 2 microns, the resistance to dislocation movement within adjacent sintered particles is enhanced, improving the mechanical properties of the sintered article.
• Such an intermediate layer may be deposited by at least one method chosen from chemical vapor deposition, physical vapor deposition, plasma deposition, laser cladding or deposition process, plasma cladding, magnetic plasma deposition, electrochemical plating, electroless plating, sputtering, solid phase synthesis, solution chemistry deposition processes, and combinations of such processes.
• the intermediate layer is deposited at a temperature that may range from 20 0 C to about 8000 0 C, such as, for example, from 20 0 C to 125°C.
• the intermediate layer is deposited at a temperature that may range from 125°C to 1800 0 C, from 1800°C to about 8000°C and further, for example, from 200°C to 800°C.
• the intermediate layer comprises a material selected from, for example, WC, TaC, W 2 C, or WC and W 2 C in an amount that may range from, for example, 60% to 98% by weight of the article.
• the intermediate layer comprises WC, TaC, W 2 C, or WC and W 2 C in an amount that may range from, for example, 10% to 60% by weight of the article.
• the intermediate layer comprises WC, TaC, W 2 C, or WC and W 2 C in an amount that may range from, for example, 5% to 10% by weight of the article.
• the majority of coated TCHP particles can then encapsulated by an outer binder layer that may, for example, be continuous.
• This layer may comprise cobalt, nickel, iron, their mixtures, their alloys, or their intermetallic compounds deposited on the outer surface of the second metal compound layer.
• the outer layer typically has a thickness after sintering in the range of from 3% to 12% of the diameter of the coated particles.
• Such outer layer may further comprise at least one layer chosen from other metals, or ceramic, binder, sintering aid, and polymeric material.
• the outer layer may be deposited by at least one of the following methods: chemical vapor deposition, physical vapor deposition, plasma deposition, laser cladding or deposition process, plasma cladding, magnetic plasma deposition, electrochemical plating, electroless plating, sputtering, solid phase synthesis, or solution chemistry deposition process, and combinations thereof.
• the previously mentioned outer layer comprises at least one compound selected from metal, ceramic, binder, sintering aid, waxes, or polymeric materials.
• binders, sintering aids, waxes, or polymeric materials coating may be accomplished by means of mixing or blending, with or without the addition of heat in the range of 50 to 15O 0 C.
• TCHP coating layers may be deposited throughout a wide range of temperatures, using many different processes, with CVD being the most common.
• the most common temperature range for CVD coating deposition is 200 0 C to 800°C.
• much higher temperatures (1800°C to about 8000 0 C) are typical for processes such as plasma deposition, magnetic plasma deposition, pulsed laser deposition and electric arc discharge.
• much lower temperatures (20 0 C to 200°C) are typical for processes such as sol-gel solution chemistry, electrochemical and electroless depositions.
• the various outer layer embodiments are deposited at different temperatures depending on the compound or compounds being deposited, the various precursors used for a given compound deposited, the layer deposition method used from the previous paragraph, the core particle chemistry, the intermediate layer thickness, and the desired properties of the coating, the outer layer may be deposited at temperatures ranging from 2O 0 C to 65O 0 C. In one embodiment, the outer layer is deposited at a temperature ranging from, for example, 20 0 C to 125 0 C. In another embodiment, the outer layer is deposited at a temperature ranging from, for example, 125 0 C to 650 0 C.
• the outer layer is deposited at a temperature that may range from, for example, 200°C to 550°C.
• the outer layer of the particle generally has a thickness after sintering in the range of from 3% to 12% of the diameter of the coated particles. The thickness of the outer layer may allow strain fields associated with dislocations in one coated particle to be transmitted through the outer binder layer to the immediately adjacent intermediate layer.
• the outer layer comprises an amount, for example, up to 45% by weight of the article and further, for example, from about 0.5% to 3.0% by weight of the article.
• the outer layer comprises an amount ranging from greater than 3.0% to 18% by weight of the article, and in yet another the outer layer comprises an amount ranging from greater than 18% to 45% by weight of the article.
• the combination of the core particles, intermediate layer, and outer layer may form a coated particle, having an average particle size of, for example, less than about 1 micron.
• a sintered TCHP embodiment comprising a plurality of sintered TCHP coated composite particle variants having a plurality of core particle compounds or elements as described above can be engineered to simultaneously reside in a common contiguous microstructure of high fracture toughness comprised of the particle intermediate coatings and binder layers.
• TCHPs are fabricated for eventual consolidatation into or clad onto articles. Consolidated TCHP articles are designed for numerous applications, such as those demanding both extreme wear resistance and high toughness.
• TCHPs are a unique material class essentially comprised of plural composite TCHP coated particles sintered into a unified whole.
• the TCHP-coated particles are sintered into articles utilizing liquid phase sintering.
• the articles are liquid phase sintered utilizing cobalt as the binder phase.
• binders In other embodiments, nickel or iron or alloys of cobalt, nickel, and iron bay be used as binders. Consolidation during this sintering process may occur primarily from capillary forces. [064] Liquid phase sintering of TCHPs may be facilitated by several factors. One factor is a substantially uniform distribution of the material comprising the outer layer throughout the powder. For purposes of describing the distribution of this material, "uniform" means that the outer layer on the surface of the intermediate layer of the particles is such that the material of the outer layer is evenly distributed throughout the body of the unsintered compacted powder.
• TCHP may be achieved, in certain embodiments, by adding cobalt (or other material comprising the outer layer on the particle) atom-by-atom during coating, to encapsulate the surface of the highly contiguously WC-coated TCHP particle with the targeted Co:WC ratio. This continues until the desired Co:WC ratio is uniformly distributed on the TCHP particles and throughout the powder.
• This feature of TCHP allows the conditions to be adapted to suit many different targeted TCHP compositions, such as, for example, by (a) protecting the core particles from dissolution by the binder and (b) providing a contiguous tough support structure.
• sintering may occur at conditions, such as temperature, and/or consolidation pressure, for a time sufficient to obtain a liquid phase in the outer layer, the intermediate layer, or both in an amount up to, for example, 99.5%, such as 70% by volume of the layers, not including the core particle volume and further, for example, up to 45% by volume of the layers, not including the core particle volume.
• sintering temperatures may range, for example, from 600 0 C to about 8000°C. In one embodiment, the sintering temperature may range from 600 0 C to 1700°C, such as, for example, from 1250 0 C to 1700 0 C.
• the sintering temperature may range, for example, from 1700°C to about 8000 0 C.
• the sintering temperature may range, for example, from 600 0 C to 1700 0 C and the amount of the liquid phase may range, for example, from 6 to 44% by volume of the layers, not including the core particle volume.
• TCHP consolidation takes place at some pressure higher than absolute zero pressure, such as in the range from zero absolute pressure to atmospheric pressure.
• the use of lower-than-atmospheric pressure is generally for two purposes: control of chemical reaction rates and control of physical processes during the various temperature ranges employed during the sintering process.
• the gases may include but are not limited to nitrogen, argon, helium, hydrogen, neon, krypton, xenon, methane, acetylene, carbon monoxide, carbon dioxide, and their mixtures and related compounds.
• pressureless sintering only refers to the sintering or consolidation at sintering temperatures, not the forming of pre- fired (or "green") articles during cold or warm compacting processes, such as cold isostatic pressing (CIP).
• Binders typically used to add green strength to articles formed from the TCHP described herein include, but are not limited to, paraffin waxes, stearic acid, ethylene bis-stearamide (EBS), plasticizers (such as polyvinyl alcohol, polyethylene glycol, or synthetic resins), and similar related organic compounds.
• the thin WC and Co TCHP coatings require protection from airborne oxygen and moisture, and this may require an additional polymeric protective coating.
• Examples of physical TCHP processes that can be controlled through use of lower-than-atmospheric pressures include transport of polymeric materials (e.g. debinding or delubing rates), volatilization rates, heat transfer rates, and possible thermal decomposition of constituent materials.
• Polymeric materials are used in these TCHP applications as fugitive binders and lubricants, for protective encapsulation, and for shelf-life enhancement, for example, include those previously mentioned, e.g., paraffin waxes, stearic acid, ethylene bis-stearamide (EBS), plasticizers (such as polyvinyl alcohol, polyethylene glycol, or synthetic resins), and similar related organic compounds.
• EBS ethylene bis-stearamide
• plasticizers such as polyvinyl alcohol, polyethylene glycol, or synthetic resins
• the volume of the liquid phase in the outer layer or the intermediate layer may be increased by increasing at least one parameter chosen, for example, from the sintering temperature, the sintering pressure, and the binder material content.
• a non-limiting example of the binder material is cobalt.
• the wetting angle of the cobalt layer on the WC coating may, for example, be small and, further, for example, may be zero.
• the cobalt in TCHP, coated directly on the WC layers need only travel extremely short distances to wet and cover the WC coatings.
• the outer layers of atoms in each WC layer first diffuse and then dissolve into the outer Co layer.
• the WC layer is uniformly dissolved from the outside inwards.
• these layers achieve thermodynamic equilibrium and liquid phase with greatly reduced cobalt mobility needed.
• cobalt does not penetrate the coatings to the core particle.
• a highly contiguous WC ( i. x) coating surface structure typical of the contiguity of CVD coatings on tool inserts and other articles may be present.
• the CVD-deposited WC (1 . X) polycrystals at deposition temperatures can be up to two orders of magnitude smaller and more tightly packed than those found in conventional milled WC-Co particles.
• the intimate proximity of cobalt to these polycrystals is such that the coating polycrystals will be dissolved uniformly around the WC coating and the equilibrium may limit grain growth.
• the polycrystals may be one order of magnitude smaller than conventional milled WC-Co polycrystals.
• grain growth up to about 1 micron may occur in zones where significant Co-pooling occurs.
• the imperviousness of the TCHP WC coatings to Co attack may be due at least partly to the following explanation. It is axiomatic that the WC and Co in TCHP will behave chemically essentially like the WC and Co in conventional hardmetal blends.
• the WC coatings of TCHP particles generally dissolve from the outside in leaving an undissolved protective and structural layer around the core particles, and re-precipitate and nucleate to reinforce the existing particle coatings or as kinetically-transported pore and interstitial filler material.
• interstitial filler means a material that fills the interstices (small spaces) between adjacent particles. Only partial dissolution of the WC coating layer in the Co binder is necessary for densification, WC re- precipitation/recrystallization, and creation of contiguous TCHP microstructural matrix integrity. The only Co and WC mobility required is that needed to transport material to fill the diminishing nearby interstitices between coated core particles.
• the initial WC coating (spherical model) will be almost 129 nm thick, and will comprise about 75 wt% of the total particle.
• Dissolution of the WC at 1500 0 C will remove only 7.9 nm, or about 6% of the coating thickness, leaving about 121 nm, or about 94% of the original coating thickness for core particle protection, inter-core particle distance uniformity, and structural toughness.
• increasing the amount of binder phase solvent present by for example, increasing the cobalt layer thickness is another feasible sintering method that can be used according to the methods described herein.
• increasing cobalt weight percentages higher than are customary in WC-Co sintering become feasible as a means of providing the needed dissolution, capillarity, WC kinetics, and densification for TCHP.
• the WC is primarily present as a tough matrix material because the real wear resistance is being provided by the core particles. Added cobalt will therefore add to the amount of liquid phase during sintering while at the same time increasing fracture toughness after cooling.
• Sintering may occur in a process chosen from sintering press, vacuum, powder injection molding, plastified extrusion, hot press, hot isostatic press (HIP), sinter-HIP, sintering furnace, laser cladding process, plasma cladding, high velocity oxygen-fueled (HVOF), spark plasma sintering, pressure plasma sintering, pressure-transmission medium, dynamic/explosive compaction, sinter forge, rapid prototyping, electron beam, and electric arc.
• HVOF high velocity oxygen-fueled
• spark plasma sintering pressure plasma sintering
• pressure-transmission medium dynamic/explosive compaction
• sinter forge rapid prototyping, electron beam, and electric arc.
• the WC coating can protect the core particles from dissolution by the binder metal and can also protect the matrix from harmful pollution such as, for example, by TiN, ZrN, NbC.
• the highly wear resistant TCHP core particles can protect the WC-Co support matrix from wear after sintering while the support matrix protects the brittle phases from fracture and pullout.
• Figure 2 depicts the sintered microstructure of a typical TCHP material. [089] The TCHP structure with small hard core particle size and tough, nanoscale shells separated by thin cobalt ligaments below one micrometer between grains, improves, for example, elasticity, hardness, fracture toughness, and strength.
• TCHP provides sinterable metal particulate materials that can be engineered to afford an optimum balance of properties, such as, for example, toughness, strength, low frictional coefficient, and hardness.
• operating improvements that can be observed in dies and other tooling fabricated from TCH P's are, for example: (a) a lower friction coefficient at the interface between the work piece and tool, yielding reduced heat, wear, and cratering, and requiring less processing power and auxiliary use of external lubricants, ultimately resulting in longer tool life and better process control; (b) a low reactivity with iron, reducing sticking and diffusion, flank, or die wear, and in turn extending the service life of the drawing die; and (c) a sintered tool microstructure in which the tough, strong coating material (e.g., WC) on the particles forms a cellular support macrostructure for the tool while, at the same time, providing a surface conforming and tightly-bound protective layer for the hard particulate cores (of, for example, TiN), holding them in position and permitting optimal exposure and hard phase retention at the wear- resistant tool surface.
• the tough, strong coating material e.g., WC
• Tool life may be enhanced by the constant renewal of surface grains that wear or are pulled away by the opposing sliding surface.
• the wear resistance and adhesion characteristics of many of the possible core materials are known from their performance in conventional materials, so their performance as core particle materials is, in light of the present disclosure, predictable. Since, in certain non-limiting embodiments, the core particles are coated with known materials (e.g., WC) blending and sintering together coated particles having several different core materials will facilitate enhancement of multiple characteristics. Accordingly, the cost of development and testing are reduced while providing a final material with unique properties.
• resultant article macrostructure is a cellular microstructure framework composed of tough, strong, tightly interbonded coated particle shells, each containing and supporting at least one material chosen from mechanically and chemically-bonded core particles, crystals, fibers, and whiskers, exposed in cross-section at the external surfaces during finish grinding and polishing.
• This principle of optimizing the combination of different materials for the core particles and the surrounding intermediate layer allows the combination of normally conflicting article performance characteristics, such as, for example, strength and hardness, at levels not achievable with conventional materials.
• This concept can give a material designer multiple tools that may be used singly or in combination and a straightforward method providing easy and total control in adapting the TCHP particle structure (intermediate layer thickness, size, and core materials) and mix (integrating different powders into tool and article zones) to meet many different unique, combined, and specialty demand conditions with a single article or tool.
• tungsten carbide tungsten carbide
• the tungsten carbide coating thickness on the particle may be increased, for example, to meet more challenging strength applications or may be decreased, for example, in more critical wear applications to solve most design challenges.
• the core particle size can readily be increased to meet more severe requirements for wear resistance or decreased for higher strength applications.
• Articles made from TCHP particles combine the best mechanical properties of strength, hardness, high elastic modulus, fracture toughness, low interaction with the work piece, and low coefficient of friction that exist separately in conventional materials into an article of unmatched combined properties. TCHPs have virtually unlimited uses in the manufacture, surface modification, or repair of components, assemblies, and machines.
• One component group includes cutting, forming, grinding, measuring, petroleum, and mining and construction tools.
• Nontool components include biomedical, military, electronic, sports, thermal management, and cosmetic applications. Extensive industrial applications will be found in the agricultural, civil, lumber and paper, petrochemical, rubber and plastic, transportation, aircraft/aerospace, maritime, architectural, and energy sectors.
• tooling such as wire drawing dies, extrusion dies, forging dies, cutting and stamping dies, forms, forming rollers, injection molds, shears, drills, milling and lathe cutters, saws, hobs, broaches, reamers, taps and dies
• individual mechanical parts such as gears, cams, journals, nozzles, seals, valve seats, pump impellers, capstans, sheaves, bearing and wear surfaces
• integrated co-sintered components to replace mating parts internal combustion engine connecting rods, bearings and/or to provide hard surface zones in powdered metal (P/M) mechanical parts substituted for forged or machined steel parts with heat treated zones, such as camshafts, transmission parts, printer/copier parts
• P/M powdered metal

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Powder Metallurgy (AREA)
• Chemically Coating (AREA)
• Compositions Of Oxide Ceramics (AREA)

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Cited By (19)

Families Citing this family (27)

Citations (5)

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• 2004
  • 2004-06-10 CA CA2570671A patent/CA2570671C/en not_active Expired - Lifetime
  • 2004-06-10 CN CN2004800437747A patent/CN1997475B/zh not_active Expired - Fee Related
  • 2004-06-10 AU AU2004321077A patent/AU2004321077B2/en not_active Ceased
  • 2004-06-10 RU RU2006145849/02A patent/RU2366539C9/ru not_active IP Right Cessation
  • 2004-06-10 BR BRPI0418870-5A patent/BRPI0418870B1/pt not_active IP Right Cessation
  • 2004-06-10 JP JP2007527166A patent/JP2008502576A/ja active Pending
  • 2004-06-10 KR KR1020077000589A patent/KR101215656B1/ko active IP Right Grant
  • 2004-06-10 MX MXPA06013640A patent/MXPA06013640A/es active IP Right Grant
  • 2004-06-10 WO PCT/US2004/018445 patent/WO2006001791A1/en active Application Filing
  • 2004-06-10 EP EP04776430A patent/EP1768804A4/de not_active Withdrawn
• 2005
  • 2005-08-10 SA SA5260249A patent/SA05260249B1/ar unknown
• 2006
  • 2006-11-28 IL IL179667A patent/IL179667A/en not_active IP Right Cessation
• 2007
  • 2007-01-10 NO NO20070168A patent/NO20070168L/no unknown

Patent Citations (5)

Non-Patent Citations (3)

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