WC-based superhard alloy powder, WC-based superhard alloy component, and method for producing WC-based superhard alloy component

Abstract

The present invention provides a WC-based superhard alloy powder, a WC-based superhard alloy component, and a method for manufacturing a WC-based superhard alloy component that can manufacture a WC-based superhard alloy component having excellent high thermal conductivity and high wear resistance. The WC-based superhard alloy powder of the present invention is characterized in that it contains at least one of Co, Fe, and Cr and WC and Cu, WC is 40% by mass or more, the content of at least one of Co, Fe, and Cr is 25% by mass or more and less than 60% by mass, and the ratio a / b of the content a of Cu to the content b of at least one of Co, Fe, and Cr satisfies 0.070≤a / b≤1.000.

Description

Technical Field

[0001] The present invention relates to WC-based superhard alloy powder, a WC-based superhard alloy component, and a method for producing a WC-based superhard alloy component. Background Art

[0002] The hot stamping method is a method of quenching the workpiece heated to a high temperature by stamping it and cooling it in the die. In the hot stamping die, in order to achieve improved hardenability and high production efficiency, it is desirable to improve the thermal conductivity of the die material. In addition, in order to reduce the damage to the die caused by the oxide scale attached to the workpiece heated to a high temperature, wear resistance is required.

[0003] For example, Patent Document 1 discloses a steel for a mold having Fe as a main component and having both thermal conductivity and wear resistance. As a material for a hot stamping mold, hot working tool steel having an excellent balance between hardness and toughness and cold working tool steel having a very high hardness are mainly used. The tool steel has excellent wear resistance, but on the other hand, since various elements are added, the improvement of thermal conductivity is limited, and further improvement of thermal conductivity is desired.

[0004] As one of the materials that take into account both thermal conductivity and wear resistance, there can be cited a composite material in which hard WC is dispersed in a metal bonding phase such as Co, that is, a superhard alloy (hereinafter referred to as WC-based superhard alloy). WC-based superhard alloys are used for cutting tools and the like due to their excellent wear resistance. On the other hand, they also have excellent thermal conductivity, and the thermal conductivity of WC-based superhard alloys is higher than that of tool steel.

[0005] As an example of WC-based superhard alloys, Patent Document 2 discloses a WC-Co superhard alloy having excellent hardness and toughness and a method for producing the same. In WC-based superhard alloys, increasing the content of a metal bonding phase is effective in improving the toughness of the WC-based superhard alloy (see Patent Document 2).

[0006] When WC-based superhard alloy is used in hot stamping die, if the hardness is too high, cracks will occur, so it is necessary to increase the amount of metal bonding phase to improve toughness. However, if the amount of metal bonding phase is increased, the problem of reduced thermal conductivity will occur. In addition, if the mold is to be formed by liquid phase sintering, which is a general forming method for superhard alloy, the forming of the complex cooling water channel structure inside is difficult, and deformation caused by deadweight occurs during sintering, and there is a problem of deformation of the cooling water channel.

[0007] In recent years, additive manufacturing (AM) has attracted attention. It manufactures three-dimensional objects by locally melting and solidifying metal powder raw materials and repeating the melting and solidification. By using additive manufacturing (referred to as layered molding in the present invention), complex shapes such as hollow shapes can be molded, so molds with complex cooling water channels can be molded.

[0008] Non-Patent Document 1 describes a technique related to laser lamination molding of a WC—Co based superhard alloy.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2017-43814

[0012] Patent Document 2: Japanese Patent Application Publication No. 2016-160500

[0013] Non-patent literature

[0014] Non-patent document 1: Kyogoku Hideki, Ikuta Akihiko, Kamimori Takeshi, Shirachi Takayuki, Yoshikawa Kenichi, and Omori Masaru, "Laser Lamination of Cemented Carbide", Kinki University Next Generation Infrastructure Research Institute Report Vol. 2 (2011) 95-100 Summary of the invention

[0015] Problems to be solved by the invention

[0016] As described above, by using WC-based superhard alloy powder and manufacturing the mold by stacking molding method, deformation during manufacturing can be suppressed. However, the reduction of thermal conductivity caused by increasing the amount of metal bonding phase remains as a problem. Therefore, when the stacking molding method is applied, the balance between high thermal conductivity and high wear resistance becomes a problem.

[0017] Therefore, the object of the present invention is to provide a WC-based superhard alloy powder, a WC-based superhard alloy component and a method for manufacturing a WC-based superhard alloy component, which can improve the thermal conductivity of a WC-based superhard alloy with a high content of a metal bonding phase, thereby being able to manufacture a WC-based superhard alloy component with excellent high thermal conductivity and high wear resistance through a stacking molding method.

[0018] Methods for solving problems

[0019] One embodiment of the WC-based superhard alloy powder of the present invention comprises at least one of Co, Fe and Cr and WC and Cu, wherein the WC is 40% by mass or more, the content of at least one of Co, Fe and Cr is 25% by mass or more and less than 60% by mass, and the ratio a / b of the content a of Cu to the content b of at least one of Co, Fe and Cr satisfies 0.070≤a / b≤1.000.

[0020] In addition, one embodiment of the WC-based superhard alloy component of the present invention is a stacked molded body, which includes a metal bonding phase composed of at least one of Co, Fe and Cr, as well as WC particles and Cu, wherein the content of WC is greater than 40 mass%, the content of at least one of Co, Fe and Cr is greater than 25 mass% and less than 60 mass%, and the ratio a / b of the content a of Cu to the content b of at least one of Co, Fe and Cr satisfies 0.070≤a / b≤1.000.

[0021] In addition, it is preferred that a Cu precipitate phase having an equivalent circle diameter of 10 nm to 50 nm is dispersed and precipitated in the metal binder phase.

[0022] In addition, it is preferred that a Cu precipitated phase having an average particle size of 1 μm to 100 μm is dispersed and precipitated in the metal binder phase.

[0023] In addition, one mode of the manufacturing method of the WC-based superhard alloy component of the present invention comprises a process of preheating a substrate composed of metal to above 350°C and a process of using a heat source to melt and solidify a superhard alloy powder and stack it on the surface of the substrate; the superhard alloy powder contains at least one of Co, Fe and Cr and WC and Cu, the WC is above 40 mass%, the content of at least one of Co, Fe and Cr is above 25 mass% and less than 60 mass%, and the ratio a / b of the content a of Cu to the content b of at least one of Co, Fe and Cr satisfies 0.070≤a / b≤1.000.

[0024] In addition, it is preferable to include a step of heat treating the cemented carbide member obtained by the above-mentioned stacking molding at 400°C or higher and lower than 1250°C.

[0025] Effects of the Invention

[0026] According to the present invention, a WC-based superhard alloy powder capable of manufacturing a WC-based superhard alloy component having high thermal conductivity and high wear resistance can be provided. In addition, a WC-based superhard alloy component and a method for manufacturing the WC-based superhard alloy component based on a stacking molding method can be provided.

[0027] Other problems, structures, and effects than those described above will become apparent from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [ Figure 1A ] Backscattered electron image (BEI) of a WC-based superhard alloy component according to one embodiment of the present invention

[0029] [ Figure 1B ] Transmission electron image of a WC-based superhard alloy component according to one embodiment of the present invention by a transmission electron microscope (STEM) and a Cu surface scan by EDX

[0030] [ Figure 1C Secondary electron image (SEI) and element surface scanning of a WC-based superhard alloy component according to an embodiment of the present invention

[0031] [ Figure 2 ] A flowchart showing an example of a method for manufacturing a WC-based superhard alloy component according to the present invention

[0032] [ Figure 3 ] A schematic diagram showing an example of a WC-based superhard alloy component of the present invention

[0033] [ Figure 4 ] An observation image based on a scanning electron microscope (SEM) showing an example of comparison of the presence or absence of heat treatment of a WC-based superhard alloy member to which Cu is added DETAILED DESCRIPTION

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in this specification, the numerical range of "to" is set to include the range of numerical values ​​before and after in the above and below manner. In addition, in the drawings, the same or similar parts are marked with the same symbols, and their description is not repeated.

[0035] The inventors studied the improvement of thermal conductivity of WC-based superhard alloys with a high content of metal bonding phase when studying how to achieve both high thermal conductivity and high wear resistance in WC-based superhard alloys. Therefore, they focused on Cu, which is easily separated from the metal bonding phase of WC-based superhard alloys and has a high thermal conductivity, and found that the thermal conductivity is improved by adding Cu.

[0036] On the other hand, it is known that WC-based superhard alloy powders with a large amount of Cu added are difficult to laminate, and after repeated in-depth research, the relationship between the appropriate component ratio of the amount of Cu that can be added to the WC-based superhard alloy and the laminated molding properties was discovered. The present invention was completed based on this knowledge.

[0037] [WC-based superhard alloy powder]

[0038] As described above, the WC-based superhard alloy powder of the present invention contains WC (tungsten carbide) and Cu (copper) which are carbides of W (tungsten) and C (carbon), and also contains at least one of Co (cobalt), Fe (iron) and Cr (chromium). At least one of Co, Fe and Cr is a raw material for the metal bonding phase of WC. In this specification, such a superhard alloy is referred to as "WC-based superhard alloy". The raw material constituting the metal bonding phase can be any element that is separated (not dissolved) from Cu in the manufacturing process of the WC-based superhard alloy described later.

[0039] WC-based superhard alloy is a composite material in which hard WC is integrated by a metal binder phase. The more WC is in a WC-based superhard alloy component, the higher the hardness is. Therefore, it is preferred that WC in a WC-based superhard alloy component contains at least 40 mass %.

[0040] By increasing the content of metal bonding phase in WC superhard alloy components, the toughness of WC superhard alloy components is improved. In the WC superhard alloy powder used for the manufacture of WC superhard alloy components, in order to make the content of metal bonding phase more than 25 mass %, the content of at least one of Co, Fe and Cr as the raw materials of metal bonding phase should be more than 25 mass %. However, if the content of metal bonding phase is excessively increased, the hardness of WC superhard alloy becomes low, and it is difficult to achieve the hardness required by molds, etc. In addition, it is difficult to suppress the reduction of hardness caused by the temperature rise in the use of molds. Therefore, in the WC superhard alloy powder of the present invention, in order to make the content of metal bonding phase less than 60 mass %, the content of at least one of Co, Fe and Cr as the raw materials of metal bonding phase should be less than 60 mass %. From the above, the content of at least one of Co, Fe and Cr is more than 25 mass % and less than 60 mass %.

[0041] From the perspective of the balance between toughness and hardness, the content of at least one of Co, Fe and Cr is more preferably 25 to 40 mass %, and even more preferably 30 to 40 mass %.

[0042] In addition, in order to measure the content of the metal binder phase in the WC-based superhard alloy powder, it is possible to use X-ray fluorescence analysis (X-Ray Fluorescence: XRF) or the like which has been conventionally used for component composition analysis of superhard alloy members.

[0043] Cu is dispersed in the metal bonding phase and plays a role in improving the thermal conductivity of the WC superhard alloy member. If the WC superhard alloy member contains Cu, the thermal conductivity can be improved, but for example, Al or the like may be contained in addition to Cu.

[0044] By adding Cu, which is easily separated from Co, Fe or Cr at low temperatures, Cu is finely dispersed in the binder phase to form fine Cu precipitated particles (equivalent circle diameter is 10nm to 50nm), and thermal conductivity is improved. In addition, if Cu is added above the solid solubility limit of Co, Fe or Cr, while being finely dispersed in the binder phase, a phase (referred to as a coarse Cu precipitation phase in the present invention) in which relatively large Cu particles (average particle size is 1μm to 100μm) are precipitated is formed, and further improvement of thermal conductivity can be expected.

[0045] On the other hand, if Cu is excessively added, the viscosity of the molten pool during the stacking molding becomes high in the manufacturing method of the WC-based superhard alloy component described later, so WC and the metal bonding phase are not mixed and become an uneven structure. In addition, pores (Porosity) are easily generated in the stacked molded product. The reason is believed to be that Cu is easy to gasify and oxides are easily formed by adding Cu.

[0046] Furthermore, in the case of stacked molding using laser, the reflectivity of the laser increases due to the increase in Cu content, so it is difficult to form a molten pool and molding becomes difficult. Therefore, the amount of Cu added is selected from more than 0.1 mass % and less than 25 mass %. Furthermore, it is necessary to make the ratio of the content a of Cu to the content b of at least one of Co, Fe and Cr appropriate. Therefore, the ratio a / b of the content a to the content b preferably satisfies 0.070≤a / b≤1.000. More preferably, it is 0.090≤a / b≤0.800, and further preferably, it is 0.140≤a / b≤0.500. It should be noted that the remainder is preferably an unavoidable impurity.

[0047] [WC-based superhard alloy components]

[0048] The observation photograph of the WC-based superhard alloy member of this embodiment is shown in Figures 1A to 1C . Figure 1A It is the backscattered electron image (BEI). Figure 1B The images are transmission electron images using a scanning transmission electron microscope (STEM) and surface scans of Cu using energy dispersive X-ray spectroscopy (EDX). Figure 1C is the secondary electron image (SEI). Figure 1BThe sample can be prepared as follows: a carbon protective film is formed on the surface of the bonding phase of the WC superhard alloy component, and the film is thinned to about 100 nm by sputtering using a Ga (gallium) ion beam. Figure 1A and Figure 1C The observation can be performed using a scanning electron microscope (Scanning Electronic Microscope: SEM).

[0049] The WC-based superhard alloy component of this embodiment is produced by laminating the above-mentioned WC-based superhard alloy powder on the surface of a substrate, and has a molten solidified structure. Figure 1A As shown, in the WC-based superhard alloy component 10, WC particles 1 are bonded by a metal bonding phase 2 composed of at least one of Co, Fe and Cr. Figure 1B As shown in FIG. 1 , relatively fine Cu precipitates 3 having an average particle size of 10 nm to 50 nm are dispersed. Figure 1C As shown, relatively coarse Cu precipitate particles 4 with an average particle size of 1 μm to 100 μm are dispersed. The detailed crystal structure of the "Cu precipitation phase" containing the Cu precipitate particles 4 is not yet clear, but it is assumed that Cu is the main body (more than 50% by mass) and has an FCC (Face-Centered Cubic) structure. It should be noted that the above-mentioned "average particle size" is a value calculated by analyzing the image obtained by EPMA (Electron Probe Micro Analyzer) or EDX (Energy Dispersive X-ray spectrometry). Specifically, it is a value obtained by binarizing the image, measuring the equivalent circle diameters of multiple particles, such as about 10 particles, and averaging them. For example, it can also be measured at 0.16 μm 2 The equivalent circle diameters of the particles observed within the range are calculated and the average value is calculated.

[0050] Fe, Cr or Co and Cu constituting the binding phase of the WC-based superhard alloy of the embodiment are solid-dissolved at high temperature, but since there is almost no solid-solubility limit at low temperature, Cu phase separates and precipitates during solidification. In addition, for example, by heat treatment at 400°C or above and below 1250°C, the Cu phase further precipitates, and further improvement of thermal conductivity can be expected. Figure 1B The nano-scale fine Cu precipitation phase 3 shown has granular Cu particles having an average particle size of 10 nm to 50 nm precipitated uniformly and at substantially equal intervals in the binder phase. Such a state is considered to be preferable in order to improve thermal conductivity.

[0051] In addition, depending on the molding conditions and Cu content, Figure 1CThe coarse Cu precipitated particles 4 (average particle size: 1 μm to 100 μm) of the order of micrometers may be dispersed, but this is also considered to contribute to the improvement of thermal conductivity. For example, it is considered that the coarse Cu particles are more easily dispersed as the Cu content increases.

[0052] The WC-based superhard alloy component of the embodiment preferably has a Vickers hardness of 500 HV or more, more preferably 550 HV or more, and most preferably 600 HV or more. In addition, the thermal conductivity is preferably 40 W / (m·K) or more, more preferably 60 W / (m·K) or more, and most preferably 70 W / (m·K) or more.

[0053] The WC-based superhard alloy member of the present embodiment has both high thermal conductivity and high wear resistance and is therefore most suitable for a die for hot stamping.

[0054] The content of the metal bonding phase in the WC-based superhard alloy component is the same as that of the WC-based superhard alloy powder, preferably 25 mass % to less than 60 mass %. Similarly, the ratio a / b of the content a of Cu to the content b of the metal bonding phase preferably satisfies 0.070≤a / b≤1.000. The content a of Cu and the content b of the metal bonding phase in the WC-based superhard alloy component are the same as those of the WC-based superhard alloy powder, and can be analyzed by fluorescent X-ray analysis, etc.

[0055] In addition, in the above-mentioned non-patent document 1, 30% by mass of Cu powder is added to WC-10% by mass of Co, the amount of the metal bonding phase is 37% by mass, and the ratio a / b of the content a of Cu to the content b of Co is 4.3, which greatly deviates from the a / b of the present invention. In this document, there is a record of "adding 30% of Cu to adjust the process conditions to form a smooth surface", but from the SEM photos of this document, it is believed that as a structure, the density needs to be further increased and the Cu fraction needs to be reduced.

[0056] [Method for manufacturing WC-based superhard alloy member]

[0057] Figure 2 FIG. 1 is a flow chart showing an example of a method for manufacturing a WC-based superhard alloy component according to the present embodiment. Figure 2 As shown, the method for manufacturing a WC-based superhard alloy component includes a preheating step (S1), a lamination molding step (S2) and a heat treatment step (S3).

[0058] WC-based superhard alloy components use WC-based superhard alloy powder to stack the entire object, or repeatedly stack the surface of the metal substrate to form a layer formed by melting and solidifying the WC-based superhard alloy powder. Usually, superhard alloys are formed by a liquid phase sintering method in which they are heated to a temperature below the melting point of the hard phase and sintered, but the WC-based superhard alloy components of this embodiment are formed by a stacking molding method, which uses high-energy heat sources such as lasers, electron beams, plasmas, and arcs to locally melt and solidify the WC-based superhard alloy powder raw materials (recorded as melting and solidification), and repeats this process to manufacture a three-dimensional shape. The WC-based superhard alloy powder of this embodiment has a large content of metal bonding phases, so if it is formed by a liquid phase sintering method, it will deform due to its own weight as described below and is difficult to shape. In this regard, the stacking molding method is instantaneous and locally melted and solidified to perform molding, so it can suppress the deformation caused by its own weight during molding.

[0059] More specifically, liquid phase sintering is performed at a high temperature of nearly 1300°C, but if the proportion of the metal bonding phase is large, the shape of the structure cannot be maintained and deformation such as collapse into a barrel shape occurs. The inventors of the present invention conducted a study and found that significant deformation occurred when the metal bonding phase was 40% by mass or more. In the present invention, since the WC-based superhard alloy component is manufactured by stacking molding instead of liquid phase sintering, the WC-based superhard alloy component can be manufactured without causing the deformation that occurs in liquid phase sintering.

[0060] Hereinafter, each step of S1 to S3 will be described in detail.

[0061] (S1) Preheating process

[0062] The preheating step S1 is a step of preheating the metal substrate to a temperature of 350°C or higher. Preheating can be performed, for example, using high-frequency induction heating, a gas burner, an infrared electric heater, a heating furnace, electron beam or laser irradiation. It should be noted that in the preheating step S1, it is more preferred to preheat the metal substrate to a temperature of 500°C or higher, and it is further preferred to preheat to a temperature of 700°C or higher. In addition, in the preheating step S1, from the viewpoint of preventing deformation caused by its own weight, it is preferred to preheat the metal substrate to a temperature of 1300°C or lower, and more preferably 1000°C.

[0063] By preheating the metal substrate to a temperature of 350°C or higher in the preheating step S1, the occurrence of cracks and peeling between the WC-based superhard alloy molding and the substrate can be suppressed in the subsequent stacking molding step S2. Specifically, by preheating the substrate to a certain temperature or higher in the preheating step S1, the temperature gradient of the WC-based superhard alloy molding and the substrate during stacking molding in the stacking molding step S2 becomes gentle, which can suppress deformation caused by thermal stress and relax residual stress. In addition, by preheating the substrate to a temperature of 500°C or higher in the preheating step S1, the tiny cracks generated in the molding part due to thermal stress can be further suppressed in the stacking molding step S2.

[0064] (S2) Lamination molding process

[0065] The stacking molding step S2 is a step of stacking the WC-based superhard alloy powder of the present invention on the surface of the above-mentioned metal substrate. The stacking molding method is not particularly limited, for example, directional energy deposition methods such as laser metal deposition, powder bed fusion bonding methods, plasma powder surfacing, etc. can be used. As a heat source, laser, electron beam, plasma and arc can be used. Among them, in particular, if it is a laser, the irradiation point can be made smaller, and in addition, it can be constructed under atmospheric pressure, so it is preferred.

[0066] WC-based superhard alloy powder can be used by putting the above-mentioned raw material powders (about 0.1 to 50 μm) containing at least one of Co, Fe or Cr and WC and Cu, and 2 mass % of paraffin relative to the total amount (100 mass %) of each raw material powder into a grinder, wet mixing with ethanol (water content less than 10%) as an auxiliary agent, and then granulating and drying with a spray dryer to obtain a granulated powder.

[0067] It should be noted that the wax in the granulated powder causes internal defects during stacking molding, so it is preferably degreased at 400-600°C. In addition, the binding force of the degreased granulated powder is weak, and it will break when the powder is supplied in the stacking molding, so it is preferable to use a powder that has been temporarily sintered at 1000°C to 1400°C to improve the binding force. Furthermore, in the case of stacking molding by powder bed fusion bonding, if the fluidity of the powder is poor, the molding accuracy becomes low. Therefore, for example, it is preferable to improve the sphericity by thermal plasma droplet smelting, which is a refining method that passes the granulated powder through a high temperature area such as plasma, so as to improve the fluidity. It should be noted that not only granulated powder can be used, but also powder produced by gas atomization method and water atomization method can be used. In order to improve the molding accuracy, the fluidity of the powder (value measured according to JIS Z2502) is preferably 10-25sec / 50g.

[0068] (S3) Heat treatment process

[0069] The heat treatment step S3 is a step of heat treating the above-mentioned metal substrate and the WC-based superhard alloy molding (superhard alloy component) at a temperature of 400°C or more and less than 1250°C. As a result, Cu dissolved in the bonding phase of the superhard alloy of the stacked molding can be precipitated to improve the thermal conductivity. The heat treatment temperature is more preferably 450°C or more and less than 1250°C, further preferably 500°C or more and less than 1250°C, and most preferably 500°C to 1200°C. The heat treatment time is preferably 1 to 12 hours, more preferably 3 to 10 hours, and most preferably 5 to 8 hours.

[0070] As the atmosphere when performing heat treatment, it can be set to vacuum or inert gas atmosphere, more preferably inert gas atmosphere. By performing heat treatment under inert gas atmosphere, it is possible to promote the precipitation of Cu at a high temperature of about 1200°C for the heat treatment temperature, and on the other hand, it is possible to suppress the gasification of Cu, that is, it is possible to easily leave the Cu precipitation phase (Cu precipitation particles) in the binding phase.

[0071] In the molten part of the stacked molding, WC dissolves in Co, so η phase (W3Co3C, W6Co6C) exists in the molded body solidified by rapid cooling. The η phase is hard and has excellent wear resistance, so it can also remain as a structure. On the other hand, since it is also a brittle phase, it is not suitable for parts that require toughness. It is known that the η phase is decomposed into WC phase and Co phase by heat treatment above 1100°C. Therefore, heat treatment above 450°C and below 1250°C is effective for the precipitation of Cu and the decomposition of the η phase.

[0072] By performing the heat treatment as described above, the Cu phase is further precipitated, and further improvement of thermal conductivity can be expected. The nano-scale fine Cu precipitated phase 3 has granular Cu particles with an average particle size of 10nm to 50nm precipitated uniformly and roughly at equal intervals in the binder phase. Such a state is considered to be preferred in order to improve thermal conductivity.

[0073] Hereinafter, the present invention will be described in more detail by way of examples and comparative examples. It should be noted that the present invention is not limited to these examples.

[0074] Example

[0075] [Production of WC-Based Superhard Alloy Members for Testing of Comparative Examples 1 and 2 and Examples 1 to 3]

[0076] Test WC-based super-hard alloy components having the component compositions (unit: mass %) shown in Table 1 described later are respectively manufactured. It should be noted that in the manufacturing method, in order to simulate the structure and characteristics of the stacked molding material accompanied by melting and solidification, a specified amount of WC powder, Co and Cu blocks are added to an alumina crucible, smelted by high-frequency melting, and then cooled in the crucible. The obtained ingot is processed into a specified shape and provided for each test. The test WC-based super-hard alloy components obtained in this way have the same molten solidification structure as the stacked molding. The solidification rate is slightly slower than that of the stacked molding, but within the range that has no significant effect on the characteristics.

[0077] [Table 1]

[0078]

[0079] In Table 1, the Co contents of Comparative Examples 1 to 2 and Examples 1 to 3 are 40 mass%, 37.5 mass%, 36.5 mass%, 35 mass% and 30 mass%, respectively. In addition, the ratio a / b of the Cu content a to the binder phase (Co) content b is 0, 0.067, 0.096, 0.143 and 0.333, respectively.

[0080] Next, a test piece was cut out from the vicinity of the center of the block of the WC-based superhard alloy member for testing, and hardness and thermal conductivity were measured. The test method is described below.

[0081] <Hardness measurement>

[0082] After cutting, the cross section was polished to a mirror surface using sandpaper and diamond abrasives, and the hardness was measured at room temperature using a Vickers hardness tester under a load of 500 gf and a holding time of 15 seconds. The measurement was performed 5 times, and the average value of the 5 times was recorded. The results of the hardness measurement are shown in Table 2 described later.

[0083] <Thermal conductivity measurement>

[0084] The thermal diffusivity α, density ρ, and specific heat c of the alloy members of the examples and comparative examples were measured, and the thermal conductivity was calculated according to the following formula (1).

[0085] [Number 1]

[0086] λ=α·ρ·c…Formula (1)

[0087] (λ: thermal conductivity, α: thermal diffusivity, ρ: density, c: specific heat)

[0088] Thermal diffusivity was measured using a Xe flash thermal diffusivity measuring device (manufactured by Bruker-axs, ​​model: Nanoflash LFA447 NETZSCH). The size of the sample used in the thermal diffusivity measurement was 9.5 mm × 9.5 mm × 1.5 mm, and it was ground to #600 using water-resistant sandpaper, and graphite fine powder was applied by spraying, blackened, and used as a sample.

[0089] The density was determined by grinding the prepared alloy to #600 sandpaper and then using a hydrometer according to the Archimedean method.

[0090] In the specific heat measurement, a differential scanning calorimeter (TA Instruments, model: DSCQ2000) was used to measure the heat flow of the disk with the sample added, the empty disk, and the disk with the sapphire added, and the specific heat was calculated by substituting the heat flow into the following formula (2). It should be noted that the sample used was a sample cut to less than 50 mg, and the reference used an empty disk. In addition, the weight of the disk used in the measurement was selected to be approximately equal.

[0091] [Number 2]

[0092]

[0093] (C p : specific heat, H: heat flow, m: mass)

[0094] The measurement results of thermal conductivity are also shown in Table 2 described later.

[0095] [Table 2]

[0096]

[0097] The results of thermal conductivity and hardness tests of Comparative Examples 1 to 2 and Examples 1 to 3 after heat treatment at 500° C. for 5 hours are shown in Table 3 below.

[0098] [Table 3]

[0099]

[0100] According to Tables 2 and 3, Comparative Example 1 is a conventional WC-based superhard alloy containing no Cu, and its hardness after heat treatment is 585 HV or more, but its thermal conductivity is lower than those of Examples 1-3.

[0101] In Comparative Example 2, the ratio a / b of the content a of Cu to the content b of the binder phase (Co) is outside the range of the present invention. Since the amount of Cu is small, the thermal conductivity is about the same as that of Comparative Example 1.

[0102] Compared with Comparative Examples 1 and 2, the thermal conductivity of Examples 1 to 3 of the present invention exceeds 40 W / (m·K), and no significant decrease in hardness is observed, and the hardness is 500 HV or more. Therefore, both high thermal conductivity and high wear resistance are satisfied. It should be noted that Examples 2 and 3 with high Cu content also confirmed the presence of 1 μm to 100 μm granular coarse Cu precipitation particles.

[0103] Furthermore, it was additionally confirmed that a good molded body could be obtained by using the WC-based superhard alloys of Examples 1 to 3 described above.

[0104] [Production of WC-Based Superhard Alloy Members by Lamination Molding in Comparative Examples 3 and 4 and Examples 4 to 10]

[0105] Next, a WC-based superhard alloy member was produced using a layer-by-layer molding method.

[0106] The WC-based cemented carbide powder used had a WC content of 60 mass%, a Co content of 40 mass%, and a Cu content of 20 mass%. The ratio a / b of the Cu content a to the binder phase (Co) content b was 0.630.

[0107] The cascade modeling method was set to directional energy deposition method, and the modeling conditions were set to output 1800W and scanning speed 800mm / min.

[0108] As a lamination molding step, first, layers formed by melting and solidifying the WC-based superhard alloy powder are repeatedly laminated on the surface of a laminated metal substrate preheated to 700° C., thereby manufacturing a WC-based superhard alloy member.

[0109] Next, several heat treatment conditions are set to heat treat the WC-based superhard alloy components. These heat treatment conditions are shown in Table 4, which are set to 1100°C for 5 hours (hr) in vacuum (Example 4), 1150°C for 5 hours in vacuum (Example 5), 1175°C for 5 hours in vacuum (Example 6), 1175°C for 5 hours in argon atmosphere (Example 7), 1175°C for 10 hours in argon atmosphere (Example 8), 1200°C for 2 hours in argon atmosphere (Example 9), and 1200°C for 5 hours in argon atmosphere (Example 10). In addition, as Comparative Example 3, heat treatment was performed under the conditions of 1250°C and 2 hours (hr) in vacuum.

[0110] Table 4 shows the results of evaluating the precipitation degree of Cu and the residual degree of η phase in Examples 4 to 10 and Comparative Example 3. Here, η phase refers to a brittle structure composed of W3Co3C and W6Co6C, which is a harmful phase. Regarding the precipitation degree of Cu and the residual degree of η phase, when the cross-section of the WC-based superhard alloy components of Examples 4 to 10 and Comparative Example 3 is observed by surface scanning of Cu based on scanning transmission electron microscopy (STEM) and energy dispersive X-ray analysis (EDX), it is determined whether the presence (precipitation) of Cu can be confirmed in the observation area, and the case where precipitation cannot be confirmed is set as "bad", the case where precipitation is set as "ok", the case where more precipitation is set as "good", and the case where further precipitation is set as "excellent".

[0111] [Table 4]

[0112]

[0113] Next, as shown in Table 5, the content of WC and Co, the content of Cu, the heat treatment conditions and the aging treatment conditions were divided into different cases to evaluate the precipitation degree of Cu and the residual degree of η phase. As a result, as shown in Table 5, even in the case of only heat treatment as in Example 13, or in the case of neither heat treatment nor aging treatment after heat treatment as in Example 14, Cu precipitation was confirmed. In addition, in the case where the amount of Cu was set to 5 mass % as in Example 11, it was confirmed that Cu remained even if aging treatment was performed in addition to heat treatment. Moreover, even in the case of aging treatment after heat treatment as in Example 12, Cu precipitation was confirmed. Comparative Example 4 is an example that does not contain Cu.

[0114] [Table 5]

[0115]

[0116] About Examples 11 to 14 and Comparative Example 4, the hardness was measured by the same measuring method as above.

[0117] As shown in Table 6, although Cu remained in Examples 11 to 14, a decrease in hardness was suppressed.

[0118] [Table 6]

[0119]

[0120] Figure 4 SEM photographs of the molded bodies of Comparative Example 4 and Example 12 are shown. It can be seen that Comparative Example 4 does not contain Cu and is composed of WC, η phase and Co phase. On the other hand, WC, η phase, Co phase and Cu phase can be confirmed in the structure of Example 13. By changing the heat treatment conditions, the residual amount of η phase can be further reduced.

[0121] As can be seen from the above, if it is the WC-based super-hard alloy component of the present embodiment, even if no heat treatment is performed and no aging treatment is performed in addition to the heat treatment, Cu particles are precipitated in the binding phase, and the result of improving the thermal conductivity is obtained. In addition, by heat treating the WC-based super-hard alloy component of the present embodiment and then performing aging treatment after the heat treatment, more Cu phases are precipitated in the binding phase, and the result of further improving the thermal conductivity is obtained.

[0122] [Preparation of a Mold Using the WC-Based Superhard Alloy Member of Example 2]

[0123] In order to confirm the effectiveness of the present invention, two molds each having cooling holes were produced by lamination molding using maraging steel as a conventional mold material and the alloy powder of Example 2. Figure 3 Schematic diagram of the test mold made by Example 2. The mold 5 has a size of 50mm×30mm×30mm, and has two water-cooling holes 6 with a diameter of 10mm in the mold 5. A plate (workpiece) with a thickness of 2mm heated to 800°C is clamped by the two manufactured molds 5, and the time until the temperature of the workpiece reaches below 200°C is measured. It should be noted that the temperature is measured by a thermocouple installed on the side of the workpiece. In the case of using maraging steel, it takes 6.6 seconds to reach 200°C. On the other hand, in the case of using the alloy of Example 2, 200°C is reached within 5.0 seconds, which can confirm the effectiveness of the present invention.

[0124] As described above, according to the present invention, it is shown that a WC-based superhard alloy powder, a WC-based superhard alloy member, and a method for producing a WC-based superhard alloy member can be provided, which can produce a WC-based superhard alloy member excellent in high thermal conductivity and high wear resistance.

[0125] In addition, the present invention is not limited to the above-mentioned embodiments. As long as it does not deviate from the main purpose of the present invention, other methods considered within the scope of the technical concept of the present invention are also included in the scope of the present invention. For example, the structures and processes illustrated in the above-mentioned embodiments can also be appropriately combined or separated according to the installation method and processing efficiency. In addition, for example, the above-mentioned embodiments and modified examples can also be combined in part or in whole within the scope of non-contradiction.

[0126] Explanation of symbols

[0127] 1…WC particles, 2…binding phase, 3…Cu precipitation phase, 4…Cu precipitation particles, 10…WC-based superhard alloy component, 5…die, 6…water cooling hole.

Claims

1. A WC-based superhard alloy powder for laminated molding, characterized in that: It is composed of WC, Cu and at least one of Co, Fe and Cr as a raw material of a metal bonding phase, In terms of mass ratio, the WC is 40 mass % or more, The content of the raw material of the metal bonding phase is 25 mass % or more and less than 60 mass %, A ratio a / b of the content a of the Cu to the content b of the raw material of the metal bonding phase satisfies 0.070≤a / b≤1.

000.

2. A WC-based superhard alloy component, characterized in that: It is a laminated body composed of WC particles, Cu and metal bonding phase. The metal bonding phase is composed of at least one of Co, Fe and Cr, The content of the WC particles is 40% by mass or more, The content of the metal bonding phase is 25 mass % or more and less than 60 mass %, The ratio a / b of the content a of the Cu to the content b of the metal bonding phase satisfies 0.070≤a / b≤1.000, Furthermore, fine Cu phases having an equivalent circle diameter of 10 nm to 50 nm are dispersed and precipitated in the metal binder phase.

3. The WC-based superhard alloy component according to claim 2, characterized in that: A coarse Cu phase having an average particle size of 1 μm to 100 μm is also dispersed and precipitated in the metal binder phase.

4. A method for manufacturing a WC-based superhard alloy component, characterized in that: have: A step of preheating a metal substrate to a temperature of 350° C. to 1300° C., and A step of using a heat source to melt and solidify WC-based superhard alloy powder to perform lamination molding on the surface of the substrate; The WC-based superhard alloy powder is composed of WC, Cu, and at least one of Co, Fe and Cr as a raw material of a metal bonding phase. The WC is 40 mass % or more, The content of the raw material of the metal bonding phase is 25 mass % or more and less than 60 mass %, The ratio a / b of the content a of the Cu to the content b of the metal bonding phase satisfies 0.070≤a / b≤1.000, Furthermore, fine Cu phases having an equivalent circle diameter of 10 nm to 50 nm are dispersed and precipitated in the metal binder phase.

5. The method for manufacturing a WC-based superhard alloy member according to claim 4, characterized in that: The method comprises the step of heat treating the WC-based superhard alloy member obtained by the stacking molding at a temperature of 400°C or higher and lower than 1250°C.

6. The method for manufacturing a WC-based superhard alloy member according to claim 5, characterized in that: The heat treatment step is performed in an inert gas atmosphere.

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