Heat treatment of cast tungsten carbide particles to improve impact resistance

Abstract

Cast tungsten carbide powder, a method for producing the powder, and raw materials containing the powder include a powder containing a tungsten carbide (monocarbide) phase and a metallic tungsten phase. Cast tungsten carbide powder may contain residual amounts of W2C (hemicarbide) phase.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application is an international application claiming priority to U.S. Provisional Application No. 63 / 462,407, filed on April 27, 2023, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] (Field of the Invention) Embodiments are directed to the effect of heat treatment of cast tungsten carbide (CTC) powder on the mechanical and tribological properties of materials.

Background Art

[0003] Commercially available cast tungsten carbide (CTC) powder is generally produced by melt - casting from a mixture of tungsten and carbon in a graphite crucible. The melt is cast and rapidly quenched in a water - cooled copper mold to form very hard carbides with a fine microstructure. This material is then crushed into finer particles having an angular shape and sieved to obtain the desired particle size range. These angular CTC particles can also be melted in a high - temperature plasma or a graphite furnace to produce spherical particles of the same material. The carbon content is generally 3.7 - 4.1 wt% C (37.0 - 39.6 at%), which approximately corresponds to the carbon content of the cubic WC1 - X phase formed at the onset of liquid solidification at about 2735 °C (see the W - C phase diagram (Figure 1)).

[0004] This cubic phase rapidly decomposes into semi - carbide W2C and monocarbide WC by a eutectoid reaction (2530 °C), thus producing a very fine feathery microstructure of both phases. According to the W - C phase diagram in Figure 1, the W2C phase is stable only at temperatures higher than 1250 °C and should convert to WC and metallic tungsten by the eutectoid reaction.

[0005] However, due to the rapid cooling rate of the manufacturing process, the W2C phase formed at high temperatures is retained after cooling to room temperature. Therefore, the typical final eutectoid microstructure of CTC after cooling consists of fine, alternating plates of metastable W2C and WC (which are stable at room temperature). The proportion of each phase in the powder is approximately 75% W2C and 25% WC.

[0006] CTC powder is used with a metal binder (matrix) to create surface hardening on steel parts using welding / cladding or brazing processes. The powder is primarily used in applications requiring good wear resistance and impact resistance, such as drill bits and stabilizers for the petroleum industry, ground engagement tools, crushing hammers and rollers in mining, rock cutting and tunnel boring, and other applications exposed to heavy abrasion.

[0007] One of the drawbacks of CTC powder is its extremely high hardness (>2300 HV), which results in a brittle material. In fact, the main phase of the carbide, W2C, is known to be harder than the WC phase but more brittle. This property reduces the fracture toughness of the carbide powder and degrades the performance of CTC powder in applications subject to impact abrasion. [Overview of the project]

[0008] The embodiment relates to CTC powder in which the brittle W2C phase is converted to the WC phase and more ductile metallic tungsten by heat treatment. In this way, CTC powder with better toughness can be obtained, and thus coatings (surface hardening) containing these carbides with improved wear resistance and impact resistance can be achieved.

[0009] According to the embodiment, heat treatment of CTC powder can have many beneficial effects on the mechanical and tribological properties of the material. Firstly, the microstructure of the carbide is improved by converting W2C (phase hemicarbide) into very fine WC (monocarbide) and metallic tungsten phases. In particular, a very fine eutectoid microstructure (small crystal size) consisting of alternating WC and W plates is thus produced by the eutectoid reaction of the metastable hemicarbide phase at temperatures below 1250°C.

[0010] Another beneficial effect of heat treatment of CTC powder is the removal of free carbon (soot) often present in standard CTC. This is because soot is a soft and brittle compound that impairs the properties of the carbide in terms of hardness, toughness, and wear resistance.

[0011] The embodiment relates to cast tungsten carbide powder containing a tungsten carbide (monocarbide) phase and a metallic tungsten phase. It may also contain a residual amount of hemicarbide (W2C) phase.

[0012] In embodiments, the shape of the CTC powder may be substantially angular or substantially spherical. Substantially angular carbides may have a ratio of a first length along the major axis to a second length along the minor axis that is greater than 1.2. Substantially spherical carbides have a ratio of a first length along the major axis to a second length along the minor axis that is 1.2 or less.

[0013] In this embodiment, the cast tungsten carbide powder has a carbon content of 3.0 to 4.5% by weight.

[0014] In one embodiment, the CTC powder contains metallic tungsten phase in a fraction of 1% to 50% by weight, preferably 5% to 50% by weight, and most preferably 10% to 50% by weight.

[0015] In the embodiment, the CTC powder, without heat treatment, has a thermal conductivity 1.1 to 3.5 times higher, preferably 1.1 to 3.0 times higher, and most preferably 1.1 to 2.5 times higher, than standard CTC carbide consisting of a monocarbide (WC) phase and a hemicarbide (W2C) phase. The thermal conductivity of the untreated powder may vary depending on factors such as the lot and morphology of the carbide. This is a characteristic calculated according to the thermal conductivity of each phase from textbooks and the phase fraction obtained from the XRD pattern. Based on the data we obtained, the thermal conductivity of the untreated CTC powder is 50.0 to 91.0 W / (mK).

[0016] In the embodiment, the CTC powder has a thermal shock resistance that is 1.1 to 8.0 times higher, preferably 1.2 to 7.0 times higher, and most preferably 1.6 to 6.5 times higher, than that of a standard CTC powder consisting of a monocarbide (WC) phase and a hemicarbide (W2C) phase without heat treatment.

[0017] The embodiment applies to raw materials comprising the above-described cast tungsten carbide powder and metal alloy.

[0018] According to the embodiment, the cast tungsten carbide powder may have one unimodal size distribution among 45-325 mesh, 45-60 mesh, 60-100 mesh, 70-200 mesh, 100-200 mesh, 100-325 mesh, 200-450 mesh, or 200-325 mesh.

[0019] According to other embodiments, the cast tungsten carbide powder may have a bimodal size distribution in non-overlapping ranges, consisting of one of the following: carbide particles of 45-60 mesh and 200-325 mesh; carbide particles of 45-60 mesh and 100-325 mesh; carbide particles of 45-60 mesh and 100-200 mesh; carbide particles of 45-60 mesh and 200-450 mesh; carbide particles of 60-100 mesh and 100-325 mesh. The coarser particles among the bimodal size distribution may constitute 30-80% by weight of the total carbide components of the raw material.

[0020] According to an embodiment, the metal alloy may include a nickel, cobalt, copper, or iron alloy.

[0021] In other embodiments, the total weight fraction may include 5 to 95 wt% carbides, preferably 50 to 90 wt% carbides, and most preferably 60 to 80 wt% carbides.

[0022] An embodiment is directed to a method of forming cast tungsten carbide powder that includes casting and rapidly cooling a mixture of tungsten and carbon in a mold to be sprayed or cooled into spherical particles while in a molten state and then mechanically grinding into angular particles, cubic WC 1-X phases, a W2C (subcarbide) phase, and a WC (monocarbide) phase. The angular particles may optionally be further spheroidized by plasma. The method further includes sieving the carbide particles, i.e., the spherical and / or angular particles, into a powder within a predetermined particle size range and heat-treating the powder to convert the W2C (subcarbide) phase in the heat-treated powder to a WC (monocarbide) and a W (metallic tungsten) phase.

[0023] For example, the heat treatment converts the W2C (subcarbide) phase in the powder to approximately 52 wt% WC (monocarbide) phase and approximately 48 wt% W metallic tungsten phase in the heat-treated powder. The heat-treated powder can have a final composition of approximately 64 wt% WC and approximately 36 wt% W. Further, the pre-heat-treated powder can also include graphite that is removed in the heat-treated powder.

[0024] According to an embodiment, the heat treatment may include exposing the powder to a temperature of at least 1000 °C and less than 1250 °C for 0.5 to 50 hours in a non-oxidizing atmosphere.

[0025] An embodiment is directed to cast tungsten carbide powder formed according to the method described above.

[0026] The embodiments are directed to a raw material including the above-described cast tungsten carbide powder and a metal alloy component. The raw material may include one of a powder raw material, a cored wire raw material, a rod raw material, or a flexible rod raw material.

[0027] According to an embodiment, when the raw material includes one of a cored wire raw material, a rod raw material, and a flexible rod raw material, the metal alloy component can exist as one of a sheath of the cored wire raw material, a rod core of the rod raw material or the flexible rod raw material, or a metal powder.

[0028] According to still another embodiment, the metal alloy component can include one of a nickel alloy, a copper alloy, a cobalt alloy, or an iron alloy. The nickel alloy can be a self-fluxing alloy including a NiCrSiB alloy or a NiSiB alloy.

[0029] Other exemplary embodiments and advantages of the present invention can be confirmed by examining the present disclosure and the accompanying drawings.

Brief Description of the Drawings

[0030] The present invention will be further described in the following detailed description with reference to a plurality of drawings referred to as non-limiting examples of exemplary embodiments of the present invention, and like reference numerals represent like parts throughout several views of the drawings. [Figure 1] Shows a carbon-tungsten phase diagram. [Figure 2] Shows a comparison of XRD diffraction patterns of angular CTC before and after heat treatment at 1225°C and an immersion time of 20 hours. [Figure 3] Shows a heat treatment sequence of CTC powder. [Figure 4] Shows a comparison of Palmqvist toughness test results of standard CTC powder and heat-treated CTC powder. [Figure 5] Graphically shows the comparative microhardness of CTC, heat-treated CTC, and MTC (100% WC) powders. [Figure 6]This shows a comparison of the microstructure of laser cladding of heat-treated CTC powder and laser cladding of standard CTC powder (METCO 7010 with a NiSiB matrix). [Figure 7] This shows a comparison of the results of rotational impact abrasion tests between a laser cladding coating containing standard CTC powder and a heat-treated CTC powder (containing 35% by weight of METCO 7010). [Modes for carrying out the invention]

[0031] The details provided herein are illustrative and intended solely for illustrative purposes of embodiments of the present invention, and are presented to provide what is considered to be the most useful and readily understandable explanation of the principles and conceptual aspects of the present invention. In this regard, no attempt has been made to provide structural details of the present invention in more detail than is necessary for a basic understanding of the present invention, and the description provided in conjunction with the drawings will make it clear to those skilled in the art how some forms of the present invention can actually be embodied.

[0032] In the embodiment, cast tungsten carbide (CTC) powder is treated to convert the brittle W2C phase into the WC phase and more ductile metallic tungsten. This heat treatment produces or yields CTC powder with better toughness than standard or unheat-treated CTC powder, and as a result, coatings (e.g., surface hardening) containing these carbides of the heat-treated CTC powder achieve both improved wear resistance and impact resistance. Complete removal of the semi-carbides is desirable, but this desirable phase conversion and complete decomposition of the semi-carbide phase requires long immersion times. The inventors have found that by employing short immersion times of 20 hours or less, the heat-treated CTC contains metallic tungsten phase in a fraction of 1% to 50% by weight, preferably 5% to 50% by weight, most preferably 10% to 50% by weight, with only semi-carbides remaining, thus obtaining the advantages sought in the embodiment.

[0033] As described herein, the shape of CTC powder can be defined by the aspect ratio of the first length along the major axis to the second length along the minor axis, or the ratio of the longest axis length to the shortest axis length. Spherical or substantially spherical particles have an aspect ratio of 1.20 or less. Angular or substantially angular particles have an aspect ratio higher than 1.2. In embodiments, both substantially spherical particles and substantially angular CTC powder can be treated by a heat treatment process.

[0034] Heat treatment of CTC powder can improve the microstructure of the carbide by converting the W2C phase (semi-carbide) into very fine WC (monocarbide) and metallic tungsten phases. The final microstructure of the carbide after heat treatment consists of WC, W2C, and tungsten phases. The fraction of tungsten phase in the CTC powder after heat treatment is in the range of 1% to 50% by weight. In one embodiment, the tungsten phase is 1% to 50% by weight. In yet another embodiment, the tungsten phase is 5% to 50% by weight. In yet another embodiment, the tungsten phase is 10% to 50% by weight.

[0035] For example, Figure 2 shows the XRD patterns of angular CTC powder before and after heat treatment. The treatment was carried out at a temperature of 1225°C for a 20-hour immersion time. Before treatment, the CTC powder consisted of W2C, WC, and black smoke phases. After treatment, the CTC powder consisted of tungsten (W) and WC phases. According to the XRD diffraction patterns and the Rietveld method, the heat-treated CTC powder consists of 59.1% WC, 40.1% tungsten, and 0.8% W2C phase.

[0036] Another beneficial effect of heat treatment of CTC powder is the removal of free carbon (soot) often present in standard CTC. This is because soot is a soft and brittle compound that impairs the properties of the carbide in terms of hardness, toughness, and wear resistance. Phase analysis by X-ray diffraction (XRD) of the CTC powder containing the soot phase was first performed, showing that after heat treatment, the soot completely reacted with tungsten to form a tungsten carbide phase (see Figure 2).

[0037] To transform the hemicarbide phase present in standard CTC powders, these powders must be subjected to heat treatment under a non-oxidizing atmosphere. The heat treatment time and temperature must be sufficiently long and high to allow the carbon diffusion rate in W2C to be sufficiently high, thereby promoting the phase transformation of metastable hemicarbides to monocarbides and metallic tungsten. Based on the CW phase equilibrium diagram in Figure 1 and different tests, the heat treatment temperature range should be above 1000°C and below 1250°C, i.e., the eutectoid temperature of the hemicarbides. Heat treatment at temperatures below 1000°C has been found not to result in the transformation of the hemicarbide phase. An exemplary heat treatment sequence is shown in Figure 3.

[0038] The duration of heat treatment at the maximum / heat treatment temperature should be between 0.5 and 50 hours to allow for the conversion of the semicarbide phase. The atmosphere inside the furnace should contain a non-oxidizing gas (e.g., argon or hydrogen) with a very low fraction of oxygen to prevent oxidation on the surface of the CTC powder during heat treatment (e.g., formation of a WO3 oxide layer above approximately 500°C).

[0039] As described above, heat treatment of CTC powder transforms the harder, more brittle semi-carbide phase into a very fine eutectoid microstructure consisting of monocarbide and ductile metallic tungsten phases. This phase transformation contributes to the improved toughness and impact resistance of heat-treated CTC powder compared to standard CTC material. This behavior was confirmed by the results of various tests and analyses to evaluate the toughness of CTC powder after heat treatment at 1225°C for 20 hours in a vacuum furnace. Figure 4 shows a comparison of Palmqvist toughness tests using a 300gf Vickers indenter with a square-based diamond pyramid indenter for standard CTC powder versus heat-treated CTC powder, showing that heat-treated CTC powder is far less prone to cracking at the corners of the indenter than standard CTC powder.

[0040] As shown in Figure 5, the hardness of the heat-treated CTC powder is approximately 200 HV higher than that of standard CTC. 0.3Low. However, compared to single-crystal tungsten carbide (MTC) containing 100% monocarbide phase (WC), heat-treated CTC powder exhibits significantly higher hardness, even when containing 60-70% monocarbide and 30-40% softer metallic tungsten phase. In this case, the extremely fine eutectoid microstructure obtained by heat treatment is clearly a contributing factor to this increase in hardness.

[0041] Similar to standard CTC powder, heat-treated CTC powder can be mixed with Ni-, Cu-, Co-, or Fe-based metal matrices to form wear-resistant metal matrix composite (MMC) coatings. A wide variety of surface hardening processes can be used to manufacture these coatings, including laser cladding, plasma transfer arc (PTA) cladding, MIG and TIG welding, oxygen-fuel brazing, and other surface hardening processes.

[0042] When cladding parts with MMC coatings containing standard CTC powder using high-heat-input welding methods, the main drawback was the thermal-induced dissolution of carbide particles in the molten bath. In fact, the metastable semi-carbide phase, which constitutes a high fraction of standard CTC particles, is known to dissolve more readily in liquid than the monocarbide phase. Dissolution of the carbide phase in the liquid metal reduces the volume fraction of primary carbides in the coating, thus negatively impacting the wear performance of the MMC coating. Furthermore, during solidification of the molten pool, W and C dissolved in the liquid metal matrix react with elements present in the liquid metal to form composite η-carbide-brittle (W,M)6C type and (W,M) 12 It tends to form precipitations of C-type carbides (M=Ni, Co, Fe, Cr...). The precipitation of these complex carbides usually increases the hardness of the metal matrix, but also increases its brittleness.

[0043] Therefore, the beneficial effect of heat treatment of CTC powder is that, compared to unheat-treated powder, there is little to no metastable semicarbide phase within the carbide, significantly reducing the formation of these brittle η-carbides in the metal matrix after cladding. This contributes to maintaining better ductility and toughness in the metal matrix.

[0044] As a result of good ductility (due to the formation of fewer brittle η-carbides) and good carbide fracture toughness of the metal matrix, MMC coatings containing heat-treated CTC powder exhibit better impact abrasion resistance compared to the same coatings containing standard CTC. The results of the rotational impact abrasion test shown in Figure 7, performed on laser cladding coatings containing 65 wt% standard and heat-treated CTC powder (-150 + 53 μm) in a Ni-based matrix, show a reduction of over 77% in impact abrasion volume loss with heat-treated CTC powder.

[0045] Another beneficial effect of MMC coatings containing heat-treated carbides is the improved high-stress wear resistance of the coating. Due to their good toughness, heat-treated CTC carbides are less prone to cracking when subjected to high-stress contact. According to the ASTM B611 standard (high-stress slurry wear test using steel wheels), a coating containing heat-treated CTC powder in a Ni-based matrix and brazed onto a steel part by oxygen fuel welding exhibits better high-stress wear resistance (54% less volume loss) than a coating with the same amount of standard CTC powder.

[0046] Another advantage of heat treatment of CTC powder is the improvement of its thermal conductivity. The thermal conductivity of the W, WC, and W2C phases is shown in Table 1. As shown in the table, the W phase has a much higher thermal conductivity than the W2C phase. Heat treatment of CTC powder results in the decomposition of W2C, which has low thermal conductivity, into the W and WC phases, which have high thermal conductivity. Therefore, the thermal conductivity of CTC powder is improved after heat treatment. The thermal conductivity of CTC powder before and after heat treatment can be calculated based on the mixing rule, the thermal conductivity of each phase, and the phase fraction obtained from the XRD pattern.

[0047] In some embodiments, the thermal conductivity of heat-treated CTC powder is 1.1 to 3.5 times higher than that of standard, untreated CTC powder. In preferred embodiments, the thermal conductivity of heat-treated CTC powder is 1.1 to 3.0 times higher than that of ordinary, untreated CTC powder. In more preferred embodiments, the thermal conductivity of heat-treated CTC powder is 1.1 to 2.5 times higher than that of ordinary, untreated CTC powder. It is understood that the thermal conductivity of untreated CTC powder may vary depending on factors such as the lot and morphology of the carbide, but it may be a property calculated according to the thermal conductivity of each phase from textbooks and the phase fraction obtained from the XRD pattern. The thermal conductivity of such CTC powder is 50.0 to 91.0 W / mK.

[0048] Another benefit of heat treatment of CTC powder is improved thermal shock resistance. According to U.S. Patent No. 10,760,343B2, thermal shock resistance (TSR) can be estimated using the following formula. Table 1 shows details of the thermomechanical properties of different W-related phases. All data were obtained from the literature. By considering the average values ​​of the properties, the TSR of each could be calculated. As can be seen from the table, the W phase has the highest TSR. The TSRs of the WC phase and W2C phase are only 13% and 7% of the TSR of W, respectively. After heat treatment, W is formed while W2C decomposes, resulting in an improvement in the TSR of the CTC powder. The TSR of CTC powder before and after heat treatment can be calculated based on the mixing rule, the phase fraction obtained from the XRD pattern, and the TSR of each W-related phase. In some embodiments, the TSR of heat-treated CTC powder is 1.1 to 8.0 times higher than that of standard, unheat-treated CTC powder, and the thermal shock resistance of unheat-treated CTC powder is 7.99 to 10.64 kWm. In some preferred embodiments, the TSR of heat-treated CTC powder is 1.2 to 7.0 times higher than that of ordinary, unheat-treated CTC powder. In some more preferred embodiments, the TSR of heat-treated CTC powder is 1.6 to 6.5 times higher than that of ordinary, unheat-treated CTC powder.

[0049]

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[0050] [Table 1] [1] Huang, S., Guo, H., Zhang, Z., Zhang, X., Xie, H., Xie, Z., Peng, L. and Mi, X., 2020. Comparative study on the properties and microscopic mechanism of Ti coating and W coating diamond-copper composites. Materials Research Express, 7(7), p.076517. [2]Tungsten carbide - Wikipedia [3] Zhang, D., Li, Z., Shan, Q., Jiang, Y., Feng, J. and Chong, X., 2020. Thermodynamic analysis of the interface reaction and thermal stress of WCp / Fe composites. Ceramics International, 46(16), pp. 26210-26215. [4] Taimatsu, H., Sugiyama, S. and Kodaira, Y., 2008. Synthesis of W2C by reactive hot pressing and its mechanical properties. Materials transactions, 49(6), pp. 1256-1261. [5] Krsjak, V., SHWei, S. Antusch, and Y. Dai. “Mechanical properties of tungsten in the transition temperature range.” Journal of Nuclear Materials 450, no. 1-3 (2014): 81-87. [6] Cardarelli, Francois. “Materials handbook: a concise desktop reference.” (2008). [7] Garcia-Ayala, E. “Aqueous colloidal processing of W and WC-based composites, sintering and mechanical properties at high temperature.” (2021).

[0051] For all these reasons, heat-treated CTC powder is well-suited for applications requiring superior wear resistance and impact wear resistance, as well as applications subject to high-stress contact on component surfaces. Applicable industries and related components include, but are not limited to, PDC drill bits, stabilizers, rotary bicone and tricone drill bits in the oil and gas industry, rock crushing hammers and rolls in mining, scraper blades, crusher jaws, teeth and blades, chute liners, impact crushers, crusher roll shells, and classification screens in the agricultural industry, plow blades, tiller blades, and peeling knives and multi-knives in forestry. Other components suitable for heat-treated carbide applications include, but are not limited to, ground engagement tools (GET), slurry pump impellers and casings, shear blades, guide rolls, sugarcane mill rollers, and conveyor screws. [Examples]

[0052] In some embodiments, heat-treated carbides can be blended with metal alloys (e.g., Ni-based alloys such as NiCrSiB and NiSiB self-fluxing alloys, as well as Cu-, Co-, or Fe-based alloys) for use as a raw material in welding processes. In some embodiments, the raw material containing heat-treated carbides may be a powder for use in laser cladding, high-speed laser cladding (EHLA), plasma transfer arc (PTA) welding, oxygen fuel / spray, and fuse cladding. In some embodiments, the raw material containing heat-treated carbides may be a cored wire for MIG, TIG, SMAW, MMAW, or FCAW welding. In some embodiments, the raw material containing heat-treated carbides may be a rod or flexible cord for oxygen fuel welding / brazing.

[0053] In some embodiments, the raw material is unimodal in size distribution. In some embodiments, the raw material can include carbide particles of 45 to 325 mesh. In some embodiments, the raw material can include carbide particles of 45 to 60 mesh. In some embodiments, the raw material can include carbide particles of 60 to 100 mesh. In some embodiments, the raw material can include carbide particles of 70 to 200 mesh. In some embodiments, the raw material can include carbide particles of 200 to 325 mesh. In some embodiments, the raw material can include carbide particles of 200 to 450 mesh. In some embodiments, the raw material can include carbide particles of 100 to 200 mesh. In some embodiments, the raw material can include carbide particles of 100 to 325 mesh.

[0054] In some embodiments, the raw material may contain two particle size modes with a bimodal distribution and therefore non-overlapping size ranges. In one embodiment, the raw material may include carbide particles of 45-60 mesh and carbide particles of 200-325 mesh. In another embodiment, the raw material may include carbide particles of 45-60 mesh and carbide particles of 200-450 mesh. In yet another embodiment, the raw material may include carbide particles of 45-60 mesh and carbide particles of 100-325 mesh. In yet another embodiment, the raw material may include carbide particles of 45-60 mesh and carbide particles of 100-200 mesh. In yet another embodiment, the raw material may include carbide particles of 40-80 mesh and carbide particles of 100-325 mesh. In yet another embodiment, the raw material may include carbide particles of 60-100 mesh and carbide particles of 100-325 mesh.

[0055] In some embodiments, the heat-treated carbide may be combined with a metallic alloy component, such as a nickel alloy (NiCrSiB or NiSiB), a cobalt alloy, a copper alloy, or an iron alloy, to constitute the final raw material form. In embodiments of powder raw materials, the metallic component may be the powder itself. In embodiments of core wire, rod, and flexible rod raw materials, the metallic component may include the core wire sheath, the rod core itself, and the metallic powder. In some embodiments, the metallic component may be a nickel alloy. In some embodiments, the nickel alloy may be a self-fluxing material. In some embodiments, the nickel alloy may be a NiCrSiB alloy. In some embodiments, the nickel alloy may be a NiSiB alloy. In some embodiments, the metallic component may be a cobalt, copper, or iron alloy. Exemplary nickel-based alloys include, but are not limited to, nickel balanced with 1% to 5% by weight of boron, 1% to 5% by weight of silicon, and optionally up to 12% by weight of chromium and / or up to 5% by weight of iron. Exemplary cobalt alloys include, but are not limited to, cobalt balanced with 25% to 30% by weight of chromium, and optionally, up to 10% by weight of tungsten, up to 5% by weight of nickel, up to 3% by weight of iron, up to 2% by weight of silicon, and / or up to 2% by weight of carbon (STELLITE 6, 12, and 21). Exemplary iron alloys include, but are not limited to, iron balanced with optionally, up to 20% by weight of chromium, up to 15% by weight of nickel, up to 2% by weight of manganese, up to 3% by weight of molybdenum, up to 1% by weight of silicon, and / or up to 0.2% by weight of carbon.

[0056] In embodiments, the carbides may constitute 5 to 95% of the total weight fraction of the final raw material form, preferably 50 to 90%, and most preferably 60 to 80% of the total weight fraction of the final raw material form.

[0057] In embodiments, the shape of the carbide may be substantially angular, substantially spherical, or a combination of the two. A substantially angular carbide has a ratio of a first length along the major axis to a second length along the minor axis of greater than 1.2. A substantially spherical carbide has a ratio of a first length along the major axis to a second length along the minor axis of 1.2 or less.

[0058] In some embodiments using a bimodal distribution, the weight fraction of large carbides is 30–80% by weight of the total carbide components of the raw material. For example, the raw material may consist of 70% by weight of carbide powder and 30% by weight of NiSiB or NiCrSiB or powder. The carbide components of this exemplary raw material may be further broken down into 66% by weight of 45–60 mesh heat-treated carbide powder and 34% by weight of 200–325 mesh heat-treated carbide powder. In another example, the carbide components in the raw material contain 57% by weight of 45–60 mesh heat-treated carbides and 43% by weight of 100–325 mesh heat-treated carbides. In yet another example, the carbide components in the raw material contain 78% by weight of 60–100 mesh heat-treated carbides and 22% by weight of 100–325 mesh heat-treated carbides. In another example, the raw materials may consist of 60% by weight of carbide powder and 40% by weight of NiCrSiB powder. The carbide component of the raw materials in this example contains 75% by weight of 45-60 mesh heat-treated carbide and 25% by weight of 100-200 mesh heat-treated carbide. In yet another example, the raw materials may consist of 65% by weight of carbide powder and 35% by weight of NiCrSiB powder. The carbide component of the raw materials in this example contains 54% by weight of 45-60 mesh heat-treated carbide and 46% by weight of 200-450 mesh heat-treated carbide. In yet another example, the carbide component contains 61.5% by weight of 45-60 mesh heat-treated carbide and 38.5% by weight of 200-450 mesh heat-treated carbide.

[0059] In some embodiments, a portion of the carbides in the raw material can be heat-treated, while the remaining portion is left in an unheated state, i.e., a standard state. In some embodiments, 10 to 100% by weight of the total carbide fraction may be heat-treated carbides, preferably 20 to 90% by weight of the total carbide fraction, and most preferably 30 to 80% by weight of the total carbide fraction.

[0060] In some embodiments, the wear-resistant layer deposited using the raw materials demonstrated above exhibits excellent high-stress wear resistance according to the ASTM B611 standard. In some embodiments, the wear-resistant layer containing heat-treated carbides is 100-400 mm thick according to the ASTM B611 standard. 3 This shows the volume loss. In some preferred embodiments, the wear-resistant layer containing heat-treated carbides is 100-300 mm thick according to the ASTM B611 standard. 3 This shows the volume loss. In a more preferred embodiment, the wear-resistant layer containing heat-treated carbides is 120-250 mm 3 This shows the volume loss.

[0061] In some embodiments, the wear-resistant layer produced using the raw materials demonstrated above provides excellent conductivity. In some embodiments, the conductivity of the wear-resistant layer containing the heat-treated carbide is 1.200 to 2.100 mS / m. In some preferred embodiments, the conductivity of the wear-resistant layer containing the heat-treated carbide is 1.300 to 2.100 mS / m. In more preferred embodiments, the conductivity of the wear-resistant layer containing the heat-treated carbide is 1.400 to 2.100 mS / m.

[0062] In some embodiments, the wear-resistant layer produced using the raw materials demonstrated above has a higher thermal conductivity than the wear-resistant layer having untreated tungsten carbide. In some embodiments, the thermal conductivity of the wear-resistant layer containing heat-treated carbide is 1.20 to 21.00 W / (mK). In some preferred embodiments, the thermal conductivity of the wear-resistant layer containing heat-treated carbide is 15.00 to 21.00 W / (mK). In more preferred embodiments, the thermal conductivity of the wear-resistant layer containing heat-treated carbide is 18.00 to 21.00 W / (mK).

[0063] In this embodiment, the wear-resistant layer manufactured using the above raw materials has higher thermal shock resistance than the wear-resistant layer made using tungsten carbide that has not undergone heat treatment.

[0064] Table 2 lists several examples of wear-resistant layers with and without heat-treated tungsten carbide, along with their associated coating properties. As shown in Table 2, all samples have a bimodal carbide distribution with a total carbide fraction of 60 wt%. All carbides in sample A were not heat-treated, resulting in the worst wear performance according to the ASTM B611 test, and the lowest thermal and electrical conductivity. In sample B, a large carbide fraction of 20% by weight was heat-treated, and the remaining carbides in the sample were standard spherical cast tungsten carbide that was not heat-treated. Sample B showed a dramatic improvement in wear performance according to the ASTM B611 standard compared to sample A. Furthermore, the electrical and thermal conductivity of sample B was also improved compared to sample A. Sample C had a larger proportion of large carbides compared to samples A and B, and all carbides in sample C were heat-treated. The wear performance, electrical conductivity, and thermal conductivity of sample C, according to the ASTM B611 standard, are further improved compared to samples A and B.

[0065] [Table 2]

[0066] It should be noted that the examples described herein are provided solely for illustrative purposes and are not intended to be construed as limitations of the invention. While the invention has been described with reference to exemplary embodiments, it should be understood that the terms used herein are descriptive and illustrative, not limiting. Modifications may be made within the scope and spirit of the appended claims, as described and amended, in such embodiments. While the invention is described herein with reference to specific means, materials, and embodiments, the invention is not intended to be limited to the details disclosed herein. Rather, the invention extends to all functionally equivalent structures, methods, and uses, such as those within the scope of the appended claims.

Claims

1. Cast tungsten carbide powder, Tungsten carbide (monocarbide) phase, metallic tungsten phase, and residual amount of hemicarbide (W ２ C) Cast tungsten carbide powder containing phase C.

2. The cast tungsten carbide powder according to claim 1, wherein the carbon content is 3.0 to 4.5% by weight.

3. The cast tungsten carbide powder according to claim 1, wherein the shape of the cast tungsten carbide powder is at least one of the following: substantially angular, having a ratio of a first length along the major axis to a second length along the minor axis of greater than 1.2; or substantially spherical, having a ratio of a first length along the major axis to a second length along the minor axis of 1.2 or less.

4. The cast tungsten carbide powder according to claim 1, wherein the powder contains 1% to 50% tungsten phase.

5. The aforementioned powder consists of a monocarbide (WC) phase and a hemicarbide (W) phase that have not undergone heat treatment. ２ The cast tungsten carbide powder according to claim 1, wherein the thermal conductivity is 1.1 to 3.5 times, preferably 1.1 to 3.0 times, and most preferably 1.1 to 2.5 times higher than that of a standard CTC carbide consisting of phase C.

6. The aforementioned powder consists of a monocarbide (WC) phase and a hemicarbide (W) phase that have not undergone heat treatment. ２ The cast tungsten carbide powder according to claim 1, which has 1.1 to 8.0 times, preferably 1.2 to 7.0 times, and most preferably 1.6 to 6.5 times higher thermal shock resistance compared to a standard CTC carbide consisting of phase C).

7. It is a raw material, A raw material comprising the cast tungsten carbide powder described in claim 1 and a metal alloy.

8. WC phase and W ２ The raw material according to claim 7, further comprising standard cast tungsten carbide powder having a C phase.

9. The raw material according to claim 8, wherein the fraction of carbides from the cast tungsten carbide powder is 10 to 100% by weight of the total carbide fraction, preferably 20 to 90% by weight of the total carbide fraction, and most preferably 30 to 80% by weight of the total carbide fraction.

10. The raw material according to claim 7, wherein the cast tungsten carbide powder has one unimodal size distribution among 45-325 mesh, 45-60 mesh, 60-100 mesh, 70-200 mesh, 100-200 mesh, 100-325 mesh, 200-325 mesh, or 200-450 mesh.

11. The raw material according to claim 7, wherein the cast tungsten carbide powder has a bimodal size distribution in non-overlapping ranges, wherein the cast tungsten carbide powder is one of the following: carbide particles of 45 to 60 mesh and carbide particles of 200 to 325 mesh; carbide particles of 45 to 60 mesh and carbide particles of 200 to 450 mesh; carbide particles of 45 to 60 mesh and carbide particles of 100 to 325 mesh; carbide particles of 40 to 80 mesh and carbide particles of 100 to 325 mesh; carbide particles of 60 to 100 mesh and particles of 100 to 325 mesh.

12. The raw material according to claim 7, wherein the shape of the cast tungsten carbide powder is at least one of the following: substantially angular, having a ratio of a first length along the major axis to a second length along the minor axis of greater than 1.2; or substantially spherical, having a ratio of a first length along the major axis to a second length along the minor axis of 1.2 or less.

13. The raw material according to claim 11, wherein the carbide particles within the upper range of the bimodal size distribution constitute 30 to 80% by weight of the total carbide components of the raw material.

14. The raw material according to claim 7, wherein the metal alloy includes nickel, cobalt, copper, or an iron alloy.

15. The raw material according to claim 7, having a total weight fraction containing 5 to 95% by weight of carbides, preferably 50 to 90% by weight of carbides, and most preferably 60 to 80% by weight of carbides.

16. A method for forming cast tungsten carbide powder, A mixture of tungsten and carbon is poured into a mold and rapidly cooled to form a cubic WC crystal. １－Ｘ Phase, W ２ The material comprises a C (semicarbide) phase and a WC (monocarbide) phase, The process involves sieving the particles of the material into powders within a predetermined particle size range, and The aforementioned powder is heat-treated, and the aforementioned W in the heat-treated powder ２ A method comprising at least partially converting a C (semicarbide) phase to a WC (monocarbide) phase and a W (metallic tungsten) phase.

17. The aforementioned cast tungsten carbide powder consists of a tungsten carbide (monocarbide) phase, a metallic tungsten phase, and a residual amount of hemicarbide (W ２ The method according to claim 16, further comprising phase C.

18. Before sieving the particles of the material, the above method is performed The method according to claim 16, further comprising at least one of the following: spraying the formed material onto spherical particles while it is in a molten state, or spraying the formed material onto spherical particles while it is in a molten state, cooling the spherical particles, and crushing the cooled spherical particles into angular particles.

19. The method according to claim 18, wherein the angular particles undergo further spheroidization.

20. The method according to claim 16, wherein the tungsten phase in the heat-treated powder is in the range of 1% to 50% by weight.

21. The method according to claim 16, wherein the powder contains black smoke before the heat treatment, and the black smoke is removed in the heat-treated powder.

22. The method according to claim 16, wherein the thermal conductivity of the heat-treated powder is 1.1 to 3.5 times, preferably 1.1 to 3.0 times, and most preferably 1.1 to 2.5 times higher than the thermal conductivity of the untreated CTC powder.

23. The method according to claim 16, wherein the thermal shock resistance of the heat-treated powder is 1.1 to 8.0 times, preferably 1.2 to 7.0 times, and most preferably 1.6 to 6.5 times higher than that of the unheat-treated CTC powder.

24. The method according to claim 16, wherein the heat treatment comprises exposing the powder to a temperature of at least 1000°C and less than 1250°C for 0.5 to 50 hours in a non-oxidizing atmosphere.

25. Cast tungsten carbide powder formed according to the method described in claim 16.

26. It is a raw material, Cast tungsten carbide powder according to claim 25, Contains metal alloy components, The raw material is a raw material composed of one of the following: a powder raw material, a cord wire raw material, a rod raw material, or a flexible rod raw material.

27. The raw material according to claim 26, wherein when the raw material includes one of the core wire raw material, the rod raw material, or the flexible rod raw material, the metal alloy component exists as one of the sheath of the core wire raw material, the rod core or the rod core of the flexible rod raw material, or metal powder.

28. The raw material according to claim 27, wherein the metal alloy component includes one of nickel alloy, copper alloy, cobalt alloy, or iron alloy.

29. A wear-resistant layer, A wear-resistant layer comprising the raw material according to claim 26, which is applied as a layer by one of the following processes: laser cladding, plasma transfer arc (PTA) cladding, MIG welding and TIG welding, oxygen acetylene spray fusing, or other surface hardening processes.

30. According to ASTM B611 standard, 100 to 400 mm ３ , preferably 100 to 300 mm ３ , most preferably 130 to 250 mm ３ The wear-resistant layer according to claim 29, having a high stress wear volume loss of

31. The wear-resistant layer according to claim 29, having an electrical conductivity of 1,200 mS / m to 2,100 mS / m, preferably 1,300 mS / m to 2,100 mS / m, and most preferably 1,400 mS / m to 2,100 mS / m.

34. The wear-resistant layer according to claim 29 has a higher thermal conductivity than a wear-resistant layer having the same composition but without heat-treated tungsten carbide, wherein the higher thermal conductivity is 1.20 to 21.00 W / (mK), preferably 15.00 to 21.00 W / (mK), and most preferably 18.00 to 21.00 W / (mK).

35. The wear-resistant layer according to claim 29 is a wear-resistant layer having the same composition but with higher thermal shock resistance than a wear-resistant layer that does not contain heat-treated tungsten carbide.

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