Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
  • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
• • 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
• • 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
  • B22F3/12—Both compacting and sintering
  • B22F3/16—Both compacting and sintering in successive or repeated steps
• • 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
  • C22C29/005—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides comprising a particular metallic binder
• • 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
• • 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
  • 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
  • C22C29/08—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 based on tungsten carbide
• • 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
  • C22C29/16—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on nitrides
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • 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
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

• Hardmetals include various composite materials and are specially designed to be hard and refractory, and exhibit strong resistance to wear. Examples of widely-used hardmetals include sintered or cemented carbides or carbonitrides, or a combination of such materials. Some hardmetals, called cermets, have compositions that may include processed ceramic particles (e.g., TiC) bonded with binder metal particles. Certain compositions of hardmetals have been documented in the technical literature. For example, a comprehensive compilation of hardmetal compositions is published in Brookes' World Dictionary and Handbook of Hardmetals, sixth edition, International Carbide Data, United Kingdom (1996) .
• Hardmetals may be used in a variety of applications. Exemplary applications include cutting tools for cutting metals, stones, and other hard materials, wire-drawing dies, knives, mining tools for cutting coals and various ores and rocks, and drilling tools for oil and other drilling applications. In addition, such hardmetals also may be used to construct housing and exterior surfaces or layers for various devices to meet specific needs of the operations of the devices or the environmental conditions under which the devices operate.
• hardmetals may be formed by first dispersing hard, refractory particles of carbides or carbonitrides in a binder matrix and then pressing and sintering the mixture. The sintering process allows the binder matrix to bind the particles and to condense the mixture to form the resulting hardmetals.
• the hard particles primarily contribute to the hard and refractory properties of the resulting hardmetals.
• the hardmetal materials described below include materials comprising hard particles having a first material, and a binder matrix having a second, different material.
• the hard particles are spatially dispersed in the binder matrix in a substantially uniform manner.
• the first material for the hard particles may include, for example, materials based on tungsten carbide, materials based on titanium carbide, and materials based on a mixture of tungsten carbide and titanium carbide.
• the second material for the binder matrix may include, among others, rhenium, a mixture of rhenium and cobalt, a nickel-based supperalloy, a mixture of a nickel- based supperalloy and rhenium, a mixture of a nickel-based supperalloy, rhenium and cobalt, and these materials mixed with other materials.
• the nickel-based supperalloy may be in the ⁇ - ⁇ ' metallurgic phase.
• the volume of the second material may be from about 3% to about 40% of a total volume of the material.
• the binder matrix may comprise rhenium in an amount greater than 25% of a total weight of the material.
• the second material may include a Ni-based supperalloy.
• the Ni-based supperalloy may include Ni and other elements such as
• Fabrication of the hardmetal materials of this application may be carried out by, according to one implementation, sintering the material mixture under a vacuum condition and performing a solid-phase sintering under a pressure applied through a gas medium.
• Advantages arising from these hardmetal materials and composition methods may include one or more of the following: superior hardness in general, enhanced hardness at high temperatures, and improved resistance to corrosion and oxidation.
• FIG. 1 shows one exemplary fabrication flow in making a hardmetal according to one implementation.
• FIG. 2 shows an exemplary two-step sintering process for processing hardmetals in a solid state.
• FIGS. 3, 4, 5, 6, 7, 8 and 9 show various measured properties of selected exemplary hardmetals.
• compositions of hardmetals are important in that they directly affect the technical performance of the hardmetals in their intended applications, and processing conditions and equipment used during fabrication of such hardmetals.
• the hardmetal compositions also can directly affect the cost of the raw materials for the hardmetals, and the costs associated with the fabrication processes. For these and other reasons, extensive efforts have been made in the hardmetal industry to develop technically superior and economically feasible compositions for hardmetals.
• This application describes, among other features, material compositions for hardmetals with selected binder matrix materials that, together, provide performance advantages.
• Material compositions for hardmetals of interest include various hard particles and various binder matrix materials.
• the hard particles may be formed from carbides of the metals in columns IVB (e.g., TiC, ZrC, HfC) , VB (e.g., VC, NbC, TaC) , and VIB (e.g., Cr 3 C 2 , Mo 2 C, WC) in the Periodic Table of Elements.
• nitrides formed by metals elements in columns IVB (e.g., TiN, ZrN, HfN) and VB (e.g., VN, NbN, and TaN) in the Periodic Table of Elements may also be used.
• one material composition for hard particles that is widely used for many hardmetals is a tungsten carbide, e.g., the mono tungsten carbide (WC) .
• nitrides may be mixed with carbides to form the hard particles. Two or more of the above and other carbides and nitrides may be combined to form WC-based hardmetals or WC- free hardmetals. Examples of mixtures of different carbides include but are not limited to a mixture of WC and TiC, and a mixture of WC, TiC, and TaC.
• the material composition of the binder matrix in addition to providing a matrix for bonding the hard particles together, can significantly affect the hard and refractory properties of the resulting hardmetals.
• the binder matrix may include one or more transition metals in the eighth column of the Periodic Table of Elements, such as cobalt (Co), nickel (Ni) , and iron (Fe), and the metals in the 6B column such as molybdenum (Mo) and chromium (Cr) . Two or more of such and other binder metals may be mixed together to form desired binder matrices for bonding suitable hard particles.
• Some binder matrices for example, use combinations of Co, Ni, and Mo with different relative weights .
• the hardmetal compositions described here were in part developed based on a recognition that the material composition of the binder matrix may be specially configured and tailored to provide high-performance hardmetals to meet specific needs of various applications.
• the material composition of the binder matrix has significant effects on other material properties of the resulting hardmetals, such as the elasticity, the rigidity, and the strength parameters (including the transverse rupture strength, the tensile strength, and the impact strength) .
• the inventor recognized that it was desirable to provide the proper material composition for the binder matrix to better match the material composition of the hard particles and other components of the hardmetals in order to enhance the material properties and the performance of the resulting hardmetals.
• these hardmetal compositions use binder matrices that include rhenium, a nickel-based supperalloy or a combination of at least one nickel-based supperalloy and other binder materials.
• binder matrices that include rhenium, a nickel-based supperalloy or a combination of at least one nickel-based supperalloy and other binder materials.
• Other suitable binder materials may include, among others, rhenium (Re) or cobalt.
• a Ni-based superalloy exhibits a high material strength at a relatively high temperature.
• the resulting hardmetal formed with such a binder material can benefit from the high material strength at high temperatures of rhenium and Ni-supperalloy and exhibit enhanced performance at high temperatures.
• compositions of the hardmetals described in this application may include the binder matrix material from about 3% to about 40% by volume of the total materials in the hardmetals so that the corresponding volume percentage of the hard particles is about from 97% to about 60%, respectively.
• the binder matrix material in certain implementations may be from about 4% to about 35% by volume out of the volume of the total hardmetal materials.
• compositions of the hardmetals may have from about 5% to about 30% of the binder matrix material by volume out of the volume of the total hardmetal materials.
• the weight percentage of the binder matrix material in the total weight of the resulting hardmetals may be derived from the specific compositions of the hardmetals.
• the binder matrices may be formed primarily by a nickel-based supperalloy, and by various combinations of the nickel-based superalloy with other elements such as Re, Co, Ni, Fe, Mo, and Cr.
• a Ni-based supperalloy of interest may comprise, in addition to Ni, elements Co, Cr, Al, Ti, Mo, W, and other elements such as Ta, Nb, B, Zr and C.
• Ni-based superalloys may include the following constituent metals in weight percentage of the total weight of the supperalloy: Ni from about 30% to about 70%, Cr from about 10% to about 30%, Co from about 0% to about 25%, a total of Al and Ti from about 4% to about 12%, Mo from about 0% to about 10%, W from about 0% to about 10%, Ta from about 0% to about 10%, Nb from about 0% to about 5%, and Hf from about 0% to about 5%.
• Ni-based superalloys may also include either or both of Re and Hf, e.g., Re from 0% to about 10%, and Hf from 0% to about 5%.
• Ni-based supperalloy with Re may be used in applications under high temperatures.
• a Ni- based supper alloy may further include other elements, such as B, Zr, and C, in small amounts.
• TaC and NbC have similar properties to a certain extent and may be used to partially or completely substitute or replace each other in hardmetal compositions in some implementations. Either one or both of HfC and NbC also may be used to substitute or replace a part or all of TaC in hardmetal designs.
• WC, TiC, TaC may be produced individually or in mixture together in a form of solid solution.
• the mixture may be selected from at least one from a group consisting of (1) a mixture of WC, TiC, and TaC, (2) a mixture of WC, TiC, and NbC, (3) a mixture of WC, TiC, and at least one of TaC and NbC, and (4) a mixture of WC, TiC, and at least one of HfC and NbC.
• a solid solution of multiple carbides may exhibit better properties and performances than a mixture of several carbides.
• hard particles may be selected from at least one from a group consisting of (1) a solid solution of WC, TiC, and TaC, (2) a solid solution of WC, TiC, and NbC, (3) a solid solution of WC, TiC, and at least one of TaC and NbC, and (4) a solid solution of WC, TiC, and at least one of HfC and NbC.
• the nickel-based superalloy as a binder material may be in a ⁇ - ⁇ ' phase where the ⁇ ' phase with a FCC structure mixes with the ⁇ phase. The strength increases with temperature within a certain extent. Another desirable property of such a Ni-based supperalloy is its high resistance to oxidation and corrosion.
• the nickel-based superalloy may be used to either partially or entirely replace Co in various Co-based binder compositions.
• the inclusion of both of rhenium and a nickel- based superalloy in a binder matrix of a hardmetal can significantly improve the performance of the resulting hardmetal by benefiting from the superior performance at high temperatures from presence of Re while utilizing the relatively low-sintering temperature of the Ni-based supperalloy to maintain a reasonably low sintering temperature for ease of fabrication.
• the relatively low content of Re in such binder compositions allows for reduced cost of the binder materials so that such materials be economically feasible.
• Such a nickel-based superalloy may have a percentage weight from several percent to 100% with respect to the total weight of all material components in the binder matrix based on the specific composition of the binder matrix.
• a typical nickel-based superalloy may primarily comprise nickel and other metal components in a ⁇ - ⁇ ' phase strengthened state so that it exhibits an enhanced strength which increases as temperature rises.
• Various nickel-based superalloys may have a melting point lower than the common binder material cobalt, such as alloys under the trade names Rene-95, Udimet-700, Udimet-720 from Special Metals which comprise primarily Ni in combination with Co, Cr, Al, Ti, Mo, Nb, W, B, and Zr.
• the nickel-based supperalloy can be used in the binder to provide a high material strength and to improve the material hardness of the resulting hardmetals, at high temperatures near or above 500 °C. Tests of some fabricated samples have demonstrated that the material hardness and strength for hardmetals with a Ni- based superalloy in the binder can improve significantly, e.g., by at least 10%, at low operating temperatures in comparison with similar material compositions without Ni-based superalloy in the binder.
• hardmetal samples with Ni-based supperalloy in the binder can exhibit a material hardness that is significantly higher than that of similar hardmetal samples without having a Ni-based supperalloy in the binder.
• Ni-based supperalloy as a binder material can also improve the resistance to corrosion of the resulting hardmetals or cermets in comparison with hardmetals or cermets using the conventional cobalt as the binder.
• a nickel-based superalloy may be used alone or in combination with other elements to form a desired binder matrix.
• Other elements that may be combined with the nickel- based superalloy to form a binder matrix include but are not limited to, another nickel-based supperalloy, other non- nickel-based alloys, Re, Co, Ni, Fe, Mo, and Cr.
• Rhenium as a binder material may be used to provide strong bonding of hard particles and in particular can produce a high melting point for the resulting hardmetal material.
• the melting point of rhenium is about 3180 °C, much higher than the melting point of 1495 °C of the commonly-used cobalt as a binder material.
• This feature of rhenium partially contributes to the enhanced performance of hardmetals with binders using Re, e.g., the enhanced hardness and strength of the resulting hardmetals at high temperatures.
• Re also has other desired properties as a binder material. For example, the hardness, the transverse rapture strength, the fracture toughness, and the melting point of the hardmetals with Re in their binder matrices can be increased significantly in comparison with similar hardmetals without Re in the binder matrices.
• a hardness Hv over 2600 Kg/mm 2 has been achieved in exemplary WC-based hardmetals with Re in the binder matrices.
• the melting point of some exemplary WC-based hardmetals, i.e., the sintering temperature, has shown to be greater than 2200 °C.
• the sintering temperature for WC-based hardmetals with Co in the binders in Table 2.1 in the cited Brookes is below 1500 °C.
• a hardmetal with a high sintering temperature allows the material to operate at a high temperature below the sintering temperature.
• tools based on such Re-containing hardmetal materials may operate at high speeds to reduce the processing time and the overall throughput of the processing.
• One potential advantage of the hardmetal compositions and the composition methods described here is that they may provide or allow for a more practical fabrication process for fabricating hardmetals with either Re or mixtures of Re with other binder materials in the binder matrices.
• this two-step process makes it possible to fabricate hardmetals where Re is more than 25% of the total weight of the resulting hardmetal.
• Such hardmetals with more than 25% Re may be used to achieve high hardness and material strength at high temperatures.
• Another limitation of using pure Re as a binder material for hardmetals is that Re oxidizes severely in air at or above about 350°C. This poor oxidation resistance may dramatically reduce the use of pure Re as binder for any application above about 300°C. Since Ni-based superalloy has exceptionally strength and oxidation resistance under 1000°C, a mixture of a Ni-based superalloy and Re where Re is the dominant material in the binder may be used to improve the strength and oxidation resistance of the resulting hardmetal using such a mixture as the binder.
• the addition of Re into a binder primarily comprised of a Ni-based superalloy can increase the melting range of the resulting hardmetal, and improve the high temperature strength and creep resistance of the Ni-based superalloy binder.
• the percentage weight of the rhenium in the binder matrix should be between a several percent to essentially 100% of the total weight of the binder matrix in a hardmetal.
• the percentage weight of rhenium in the binder matrix should be at or above 5%.
• the percentage weight of rhenium in the binder matrix may be at or above 10% of the binder matrix.
• the percentage weight of rhenium in the binder matrix may be at or above 25% of the total weight of the resulting hardmetal.
• Hardmetals with such high concentration of Re may be fabricated at relatively low temperatures with a two-step process described in this application.
• a hardmetal composition includes dispersed hard particles having a first material, and a binder matrix having a second, different material that includes rhenium, where the hard particles are spatially dispersed in the binder matrix in a substantially uniform manner.
• the binder matrix may be a mixture of Re and other binder materials to reduce the total content of Re to in part reduce the overall cost of the raw materials and in part to explore the presence of other binder materials to enhance the performance of the binder matrix.
• binder matrices having mixtures of Re and other binder materials include, mixtures of Re and at least one Ni-based supperalloy, mixtures of Re, Co and at least one Ni-based supperalloy, mixtures of Re and Co, and others.
• TABLE 1 lists some examples of hardmetal compositions of interest.
• WC-based compositions are referred to as “hardmetals” and the TiC-based compositions are referred to as "cermets.”
• TiC particles bound by a mixture of Ni and Mo or a mixture of Ni and Mo 2 C are cermets.
• Cermets as described here further include hard particles formed by mixtures of TiC and TiN, of TiC, TiN, WC, TaC, and NbC with the binder matrices formed by the mixture of Ni and Mo or the mixture of Ni and Mo 2 C.
• three different weight percentage ranges for the given binder material in the are listed.
• the binder may be a mixture of a Ni-based supperalloy and cobalt, and the hard particles may a mixture of WC, TiC, TaC, and NbC.
• the binder may be from about 2% to about 40% of the total weight of the hardmetal. This range may be set to from about 3% to about 35% in some applications and may be further limited to a smaller range from about 4% to about 30% in other applications.
• Fabrication of hardmetals with Re or a nickel-based supperalloy in binder matrices may be carried out as follows. First, a powder with desired hard particles such as one or more carbides or carbonitrides is prepared. This powder may include a mixture of different carbides or a mixture of carbides and nitrides. The powder is mixed with a suitable binder matrix material that includes Re or a nickel-based supperalloy. In addition, a pressing lubricant, e.g., a wax, may be added to the mixture.
• a pressing lubricant e.g., a wax
• the mixture of the hard particles, the binder matrix material, and the lubricant is mixed through a milling or attriting process by milling or attriting over a desired period, e.g., hours, to fully mix the materials so that each hard particle is coated with the binder matrix material to facilitate the binding of the hard particles in the subsequent processes.
• the hard particles should also be coated with the lubricant material to lubricate the materials to facilitate the mixing process and to reduce or eliminate oxidation of the hard particles.
• pressing, pre-sintering, shaping, and final sintering are subsequently performed to the milled mixture to form the resulting hardmetal.
• the sintering process is a process for converting a powder material into a continuous mass by heating to a temperature that is below the melting temperature of the. hard particles and may be performed after preliminary compacting by pressure. During this process, the binder material is densified to form a continuous binder matrix to bind hard particles therein. One or more additional coatings may be further formed on a surface of the resulting hardmetal to enhance the performance of the hardmetal.
• FIG. 1 is a flowchart for this implementation of the fabrication process. [0037]
• the manufacture process for cemented carbides includes wet milling in solvent, vacuum drying, pressing, and liquid-phase sintering in vacuum.
• the temperature of the liquid-phase sintering is between melting point of the binder material (e.g., Co at 1495°C) and the eutectic temperature of the mixture of hardmetal (e.g., WC-Co at 1320 °C) .
• the sintering temperature of cemented carbide is in a range of 1360 to 1480°C.
• manufacture process is same as conventional cemented carbide process.
• the principle of liquid phase sintering in vacuum is applied in here.
• the sintering temperature is slightly higher than the eutectic temperature of binder alloy and carbide.
• the sintering condition of P17 25% of Re in binder alloy, by weight ) is at 1700 °C for one hour in vacuum.
• FIG. 2 shows a two-step fabrication process based on a solid-state phase sintering for fabricating various hardmetals described in this application.
• hardmetals that can be fabricated with this two-step sintering method include hardmetals with a high concentration of Re in the binder matrix that would otherwise require the liquid-phase sintering at high temperatures.
• This two-step process may be implemented at relatively low temperatures, e.g., under 2200 °C, to utilize commercially feasible ovens and to produce the hardmetals at reasonably low costs.
• the liquid phase sintering is eliminated in this two-step process because the liquid phase sintering may not be practical due to the generally high eutectic temperatures of the binder alloy and carbide. As discussed above, sintering at such high temperatures requires ovens operating at high temperatures which may not be commercially feasible.
• the first step of this two-step process is a vacuum sintering where the mixture materials for the binder matrix and the hard particles are sintered in vacuum.
• the mixture is initially processed by, e.g., wet milling, drying, and pressing, as performed in conventional processes for fabricating cemented carbides.
• This first step of sintering is performed at a temperature below the eutectic temperature of the binder alloy and the hard particle materials to remove or eliminate the interconnected porosity.
• the second step is a solid phase sintering at a temperature below the eutectic temperature and under a pressured condition to remove and eliminate the remaining porosities and voids left in the sintered mixture after the first step.
• a hot isostatic pressing (HIP) process may be used as this second step sintering. Both heat and pressure are applied to the material during the sintering to reduce the processing temperature which would otherwise be higher in absence of the pressure.
• a gas medium such as an inert gas may be used to apply and transmit the pressure to the sintered mixture.
• the pressure may be at or over 1000 bar.
• Application of pressure in the HIP process lowers the required processing temperature and allows for use of conventional ovens or furnaces.
• the temperatures of solid phase sintering and HIPping for achieving fully condensed materials are generally significantly lower than the temperatures for liquid phase sintering.
• the sample P62 which uses pure Re as the binder may be fully densified by vacuum sintering at
• the use of ultra fine hard particles with a particulate dimension less than 0.5 micron can reduce the sintering temperature for fully densifying the hardmetals (fine particles are several microns in size) .
• the use of such ultra fine WC allows for sintering temperatures to be low, e.g., around 2000 °C. This two-step process is less expensive than the ROC method and may be used to commercial production.
• TABLE 2 provides a list of code names (lot numbers) for some of the constituent materials used to form the exemplary hardmetals, where HI represents rhenium, and Ll, L2, and L3 represent three exemplary commercial nickel-based supperalloys .
• TABLE 3 further lists compositions of the above three exemplary nickel-based supperalloys, Udimet720 (U720) , Rene'95(R-95) , and Udimet700 (U700) , respectively.
• the material composition for Lot P17 primarily includes 88 grams of T32 (WC) , 3 grams of 132 (TiC) , 3 grams of A31 (TaC), 1.5 grams of Hi (Re) and 4.5 grams of L2 (R-95) as binder, and 2 grams of a wax as lubricant.
• Lot P58 represents a hardmetal with a nickel-based supperalloy L2 as the only binder material without Re.
• FIGS. 3 through 8 show measurements of selected hardmetal samples of this application.
• FIGS. 3 and 4 show measured toughness and hardness parameters of some exemplary hardmetals for the steel cutting grades.
• FIGS. 5 and 6 show measured toughness and hardness parameters of some exemplary hardmetals for the non-ferrous cutting grades. Measurements were performed before and after the solid-phase sintering HIP process and the data suggests that the HIP process significantly improves both the toughness and the hardness of the materials.
• FIG. 7 shows measurements of the hardness as a function of temperature for some samples.
• FIGS. 7 and 8 also show measurements of commercial C2 and C6 carbides under the same testing conditions, where FIG. 7 shows the measured hardness and FIG. 8 shows measured change in hardness from the value at the room temperature (RT) .
• RT room temperature
• the first category uses a binder matrix having pure Re
• the second category uses a binder matrix having a Re-Co alloy
• the third category uses a binder matrix having a Ni- based superalloy
• the fourth category uses a binder matrix having an alloy having a Ni-based superalloy in combination with of Re with or without Co.
• hard and refractory particles used in hardmetals of interest may include, but are not limited to, Carbides, Nitrides, Carbonitrides, Borides, and Suicides.
• Carbides include WC, TiC, TaC, HfC, NbC, Mo 2 C, Cr 2 C 3 , VC, ZrC, B 4 C, and SiC.
• Nitrides include TiN, ZrN, HfN, VN, NbN, TaN, and BN.
• Examples of Carbonitrides include Ti(C,N), Ta(C,N), Nb(C,N), Hf(C,N), Zr(C,N), and V(C,N).
• Borides include TiB 2 , ZrB 2 , HfB 2 , TaB 2 , VB 2 , MoB 2 , WB, and W 2 B.
• the Re may be approximately from 5% to 40% by volume of all material compositions used in a hardmetal or cermet.
• the sample with a lot No. P62 in TABLE 4 has 10% of pure Re, 70%of WC, 15% of TiC, and 5% of TaC by volume. This composition approximately corresponds to 14.48% of Re, 75.43% of WC, 5.09% of TiC and 5.0% of TaC by weight.
• the Specimen P62-4 was vacuum sintered at 2100 °C for about one hour and 2158 °C for about one hour.
• the density of this material is about 14.51g/cc, where the calculated density is 14.50 g/cc.
• the average hardness Hv is 2627+35 Kg/mm 2 for 10 measurements taken at the room temperature under a load of 10 Kg.
• the measured surface fracture toughness K sc is about 7.4 xlO 6 Pa-m 12 estimated by Palmvist crack length at a load of 10 Kg.
• P66 in TABLE 4 This sample has about 20% of Re, 60% of WC, 15% of TiC, and 5% of TaC by volume in composition. In the weight percentage, this sample has about 27.92% of Re, 62.35% of WC, 4.91% of TiC, and 4.82% of TaC.
• the Specimen P66-4 was first processed with a vacuum sintering process at about 2200 °C for one hour and was then sintered in the solid-phase with a HIP process to remove porosities and voids. The density of the resulting hardmetal is about 14.40g/cc compared to the calculated density of 15.04g/cc.
• the average hardness Hv is about
• the sample P66 and other compositions described here with a high concentration of Re with a weight percentage greater than 25%, as the sole binder material or one of two or more different binder materials in the binder, may be used for various applications at high operating temperatures and may be manufactured by using the two-step process based on solid-phase sintering.
• Re bound multiples types of hard refractory particles such as carbides, nitrides, carbonnitrides, suicides, and bobides
• Re-bound WC material may provide advantages over Re-bound WC material.
• Re bound WC-TiC-TaC may have better crater resistance in steel cutting than Re bound WC material.
• Another example is materials formed by refractory particles of Mo 2 C and TiC bound in a Re binder.
• the Re-Co alloy may be about from 5 to 40 Vol% of all material compositions used in the composition.
• the Re-to-Co ratio in the binder may vary from 0.01 to 0.99 approximately.
• Inclusion of Re can improve the mechanical properties of the resulting hardmetals, such as hardness, strength and toughness special at high temperature compared to Co bounded hardmetal. The higher Re content is the better high temperature properties are for most materials using such a binder matrix.
• the sample P31 in TABLE 4 is one example within this category with 2.5% of Re, 7.5% of Co, and 90% of WC by volume, and 3.44% of Re, 4.40% of Co and 92.12% of WC by weight.
• the Specimen P31-1 was vacuum sintered at 1725C for about one hour, slight under sintering with some porosities and voids.
• the density of the resulting hardmetal is about 15.16 g/cc (calculated density at 15.27 g/cc) .
• the average hardness Hv is about 1889+18 Kg/mm 2 at the room temperature under 10 Kg and the surface facture toughness K sc is about 7.7 xlO 6 Pa- ⁇ r ⁇ 2 .
• the Specimen P31-1 was treated with a hot isostatic press (HIP) process at about 1600C / 15Ksi for about one hour after sintering.
• HIP hot isostatic press
• the HIP reduces or substantially eliminates the porosities and voids in the compound to increase the material density.
• the measured density is about 15.25g/cc (calculated density at 15.27 g/cc).
• the measured hardness Hv is about 1887+12 Kg/mm 2 at the room temperature under 10 Kg.
• the surface fracture toughness K sc is aobut 7.6 xlO 6 Pa*m 1/2 .
• Another example in this category is P32 in TABLE 4 with 5.0% of Re, 5.0% of Co, and 90% of WC in volume (6.75% of Re, 2.88% of Co and 90.38% of WC in weight).
• the Specimen P32-4 was vacuum sintered at 1800C for about one hour.
• the measured density is about 15.58 g/cc in comparison with the calculated density at 15.57 g/cc.
• the measured hardness Hv is about 2065 Kg/mm 2 at the room temperature under 10 Kg.
• the surface fracture toughness K sc is about 5.9 xlO 6 Pa-m 1 2 .
• the Specimen P32-4 was also HIP at 1600C / 15Ksi for about one hour after Sintering.
• the measured density is about 15.57g/cc
• the average hardness Hv is about 2010+12 Kg/mm 2 at the room temperature under 10 Kg.
• the surface fracture toughness K sc is about 5.8 xlO 6 Pa-m 1/2 .
• the third example is P33 in TABLE 4 which has 7.5% of Re, 2.5% of Co, and 90% of WC by volume and 9.93% of Re, 1.41% of Co and 88.66% of WC by weight.
• the Specimen P33-7 was vacuum sintered at 1950C for about one hour and was under sintering with porosities and voids.
• the measured density is about 15.38 g/cc (calculated density at 15.87 g/cc).
• the measured hardness Hv is about 2081 Kg/mm 2 at the room temperature under a force of 10 Kg.
• the surface fracture toughness Ksc is about 5.6 xlO 6 Pa-m 1 2 .
• the Specimen P33-7 was HIP at 1600C / 15Ksi for about one hour after Sintering.
• the measured density is about 15.82g/cc
• the average hardness Hv is measured at about 2039+18 Kg/mm 2 at the room temperature under 10 Kg.
• the surface fracture toughness Ksc is about 6.5 xlO 6 Pa-m 1/2 .
• the samples P55, P56, P56A, and P57 in TABLE 4 are also examples for the category with a Re-Co alloy as the binder matrix. These samples have about 1.8% of Re, 7.2% of Co, 0.6% of VC except that P57 has no VC, and finally WC in balance. These different compositions are made to study the effects of hardmetal grain size on Hv and Ksc. TABLE 5 lists the results .
• Ni-based superalloys are a family of high temperature alloys with ⁇ ' strengthening. Three different strength alloys, Rene' 95, Udimet 720, and Udimet 700 are used as examples to demonstrate binder strength effects on mechanical properties of hardmetals.
• the Ni-based superalloys have a high strength specially at elevated temperatures. Also, these alloys have good environmental resistance such as resistance to corrosion and oxidation at elevated temperature. Therefore, Ni-based superalloys can be used to increase the hardness of Ni-based superalloy bound hardmetals when compared to Cobalt bound hardmetals. Notably, the tensile strengths of the Ni-based supperalloys are much stronger than the common binder material cobalt as shown by TABLE 6. This further shows that Ni-based supperalloys are good binder materials for hardmetals.
• P58 in TABLE 4 which has 7.5% of Rene' 95, 0.6% of VC, and 91.9% of WC in weight and compares to cobalt bound P54 in TABLE 4 (8% of Co, 0.6% of VC, and 91.4% of WC) .
• the hardness of P58 is significant higher than P54 as shown in TABLE 7.
• the fourth category is Ni-based superalloy plus Re as binder, e.g., approximately from 5% to 40 % by volume of all materials in the resulting hardmetal or cermet. Because addition of Re increases the melting point of binder alloy of Ni-based superalloy plus Re, the processing temperature of hardmetal with Ni-based superalloy plus Re binder increases as the Re content increases. Several hardmetals with different Re concentrations are listed in TABLE 8. TABLE 9 further shows the measured properties of the hardmetals in TABLE 8.
• Ni-based superalloy plus Re and Co as binder which is also about 5% to 40% by volume.
• Exemplary compositions of hardmetals bound by Ni-based superalloy plus Re and Co are list in TABLE 10. TABLE 10 Composition of hardmetals bound by Ni-based superalloy plus Re and Co
• Ni-based supperallosy not only exhibit excellent strengths at elevated temperatures but also possess outstanding resistances to oxidation and corrosion at high temperatures.
• Ni-based superalloys have complex icrostructures and strengthening mechanisms. In general, the strengthening of Ni-based superalloys is primarily due to precipitation strengthening of ⁇ - ⁇ ' and solid-solution strengthening. The measurements the selected samples demonstrate that Ni-based supperalloys can be used as a high- performance binder materials for hardmetals.
• TABLE 11 lists compositions of selected samples by their weight percentages of the total weight of the hardmetals.
• the WC particles in the samples are 0.2 ⁇ m in size.
• TABLE 12 lists the conditions for the two-step process performed and measured densities, hardness parameters, and toughness parameters of the samples.
• the sample P54 uses the conventional binder consisting of Co.
• the Ni-supperalloy R-95 is used in the sample P58 to replace Co as the binder in the sample P54.
• the Hv increases from 2090 of P54 to 2246 of P58.
• the mixture of Re and Co is used to replace Co as binder and the corresponding Hv increases from 2090 of P54 to 2133 of P56.
• the samples P72, P73, P74 have the same Re content but different amounts of Co and R95.
• the mixtures of Re, Co, and R95 are used in samples P73 and P74 to replace the binder having a mixture of Re and Co as the binder in the sample 72.
• the hardness Hv increases from 2041 (P72) to 2217 (P73) and 2223 (P74).
• TABLE 15 further shows measured hardness parameters under various temperatures for the selected samples, where the Knoop hardness H k were measured under a load of 1 Kg for 15 seconds on a Nikon QM hot hardness tester and R is a ratio of H k at an elevated testing temperature over H k at 25 °C.
• the hot hardness specimens of C2 and C6 carbides were prepared from inserts SNU434 which were purchased from MSC Co. (Melville, NY) . TABLE 15 (each measured value at a given temperature is an averaged value of 3 different measurements)
• the inclusion of Re in the binder matrices of the hardmetals increases the melting point of binder alloys that include Co-Re, Ni superalloy-Re, Ni superalloy-Re-Co.
• the melting point of the sample P63 is much higher than the temperature of 2200 °C used for the solid-phase sintering process.
• Hot hardness values of such hardmetals with Re in the binders e.g., P17 to P63
• the above measurements reveal that an increase in the concentration of Re in the binder increases the hardness at high temperatures.
• the sample P62A with pure Re as the binder has the highest hardness.
• the sample P63 with a binder composition of 94% of Re and 6 % of the Ni-based supperalloy R95 has the second highest hardness.
• the samples P40 (71.9%Re-29.1%R95) , P49 (69.9%Re-30.1%R95) , P51 (88.5%Re-11.5%R95) , and P50 (71.9%Re-28.1%R95) are the next group in their hardness.
• the sample P48 with 62.5% of Re and 37.5% of R95 in its binder has the lowest hardness at high temperatures among the tested materials in part because its Re content is the lowest.
• a hardmetal or cermet may include TiC and TiN bonded in a binder matrix having Ni and Mo or Mo 2 C.
• the binder Ni of cermet can be fully or partially replaced by Re, by Re plus Co, by Ni-based superalloy, by Re plus Ni-based superalloy, and by Re plus Co and Ni-based superalloy.
• P38 and P39 are a typical Ni bound cermet.
• the sample P34 is Rene95 bound Cermet.
• compositions for hardmetals or cermets may be used for a variety of applications.
• a material may be used to form a wear part in a tool that cuts, ' grinds, or drills a target object by using the wear part to remove the material of the target object.
• a tool may include a support part made of a different material, such as a steel. The wear part is then engaged to the support part as an insert.
• the tool may be designed to include multiple inserts engaged to the support part.
• some mining drills may include multiple button bits made of a hardmetal material. Examples of such a tool includes a drill, a cutter such as a knife, a saw, a grinder, a drill.
• hardmetals descried here may be used to form the entire head of a tool as the wear part for cutting, drilling or other machining operations.
• the hardmetal particles may also be used to form abrasive grits for polishing or grinding various materials.
• such hardmetals may also be used to construct housing and exterior surfaces or layers for various devices to meet specific needs of the- operations of the devices or the environmental conditions under which the devices operate.
• the hardmetals described here may be used to manufacture cutting tools for machining of metal, composite, plastic and wood.
• the cutting tools may include indexable inserts for turning, milling, boring and drilling, drills, end mills, reamers, taps, hobs and milling cutters. Since the temperature of the cutting edge of such tools may be higher than 500 °C during machining, the hardmetal compositions for high-temperature operating conditions described above may have special advantages when used in such cutting tools, e.g., extended tool life and improved productivity by such tools by increasing the cutting speed.
• the hardmetals described here may be used to manufacture tools for wire drawing, extrusion, forging and cold heading. Also as mold and Punch for powder process.

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