TW201619406A - Refractory metal-cemented fused carbides - Google Patents

Abstract

A kind of refractory metal-cemented fused carbides, comprising four kinds of strengthened phase compounds and at least one kind of refractory metal-cemented phase that are binded through the fused method for producing a refractory metal-cemented fused carbides. Based on the fused method for binding the strengthened phase and cemented phase, it can overcome the problems in the prior art in which low density and high cost occur in the sintering process, and produce a composite material having high hardness, high melting point and high toughness. When compared with conventional sintered ceramic-metal composite material, the refractory metal-cemented fused carbides of the present invention have advantages of fast, convenient, of 100% of density, and excellent hardness and toughness, and these advantages are comparatively favorable to conventional sintered composite material, or even far beyond.

Description

Refractory metal cemented carbide

The invention relates to a refractory metal cemented molten carbide, in particular to a cemented phase of a multi-component strengthening phase compound and a finite element refractory metal, which are combined in a molten manner to form a dendritic and inter-dendritic crystal. Composite structure.

Cemented carbide is a composite of WC + Co. As early as the early nineteenth century, the Frenchman Henri Moissan first synthesized tungsten carbide (WC). Tungsten carbide has a high hardness. It was originally used as a substitute for diamonds. However, it was inconvenient to be used for engineering due to the fragility and the disadvantages of holes. By 1923, Schröter and Baumhauer discovered that tungsten carbide and cobalt or nickel were combined by sintering process. At the same time, it preserves the hardness of the ceramic material and the toughness of the metal. It has a huge impact on the mold industry and is widely used in cutting tools, mining, and parts of military weapons. Using demand, we are growing rapidly year by year. In 1930, the usage was 10 metric tons. By 2008, the usage amounted to 50,000 metric tons, which was 5,000 times in 78 years. About 60% of the raw material tungsten is used in the production of cemented carbide.

The cemented carbide consists of two parts, one for the strengthening phase and the other for the cement phase. As mentioned above, tungsten carbide WC plays the role of strengthening phase, with high melting point, high toughness, good anti-wear, etc., while cobalt is a cemented phase, which has good electrical and thermal conductivity of metal. The most important feature, toughness, makes the composite less fragile.

In recent years, most of the research is based on the WC + Co system, and the strengthening phase is derived from TiC, TaC, etc., and the cemented phase is derived from Mo, Ni, Fe, etc., and these are commonly referred to as "Cermet composite materials"; The traditional Hard metal hard metal, including porcelain gold and porcelain gold composite material, the production process is sintering method, and the cemented phase is multi-encapsulated and highly entropic; and the main production method used for various sintered cemented carbides is sintering. The metallographic microstructure of the sintering method is mainly a micron-sized fine particle structure of a carbide (for example, tungsten carbide WC) and a cemented metal (for example, cobalt Co), and the porosity is not zero, and the toughness is poor, which is because sintering is performed at 1600 ° C. The micron-sized fine particle structure of tungsten carbide WC and cobalt Co will have a higher hardness and strength relationship; however, if the 3500 ° C melting method is used, it will easily cause the coarse microstructure of the material, and the hardness and The strength is reduced. Therefore, various cemented carbide composite materials are now produced by sintering.

Although the products made by the conventional sintering method still have high low-temperature hardness and low-temperature strength, the sintering process is delicate and complicated, and the toughness of the produced product is poor. In addition, the use of high-temperature refractory cement metal can improve the product. The melting point, which will increase the high temperature hardness and high temperature strength; but if the cemented metal is a high temperature refractory metal as a material for the sintering process, since the sintering process is difficult to make the refractory metal in a liquid state, the sintering method is used for high temperature. It is very difficult to refract the refractory metal.

Therefore, in order to use a high-temperature refractory metal as a cement metal, the present invention uses a smelting method to smelt a compound with a high-temperature refractory metal, in addition to maintaining a high melting point, the resulting composite material has In addition to the advantages of anti-potential change, high melting point, high hardness, high strength and high toughness, the smelting method is relatively simple and fast than the sintering method, and the metallographic microstructure of the product obtained by the smelting method is a typical branch phase and The interphase structure of the branches, with zero porosity and good toughness, should be an optimal solution.

The invention relates to a refractory metal cemented molten carbide, which is capable of bonding a multi-component strengthening phase compound and a finite element refractory metal cementation phase in a fusion manner to form a composite structure having dendrites and inter-dendritic crystals.

A refractory metal cemented fused carbide comprising: at least four reinforcing phase compounds and at least one refractory metal cement phase, wherein the reinforced phase compound and the refractory metal cement phase are combined in a molten manner to form a refractory Metal cemented carbides.

More specifically, the reinforcing phase compound used is TiC, ZrC, NbC, VC, TaC, WC, HfC, TiN or ZrN, and is capable of selecting at least four or more of the above-mentioned strengthening phase compounds and being fire resistant. The metal cement phase is combined in a molten manner.

More specifically, the refractory metal cement phase used is Mo, W, Nb, Hf, Ta or Re, and at least one of the refractory metal cemented phases can be selected for bonding with the strengthening phase compound.

More specifically, the melting mode is vacuum arc melting at a temperature exceeding 3500 degrees Celsius, so that the prepared refractory metal cemented molten carbide is a composite structure having dendrites and interdendritic crystals.

Other details, features, and advantages of the present invention will be apparent from the following description of the preferred embodiments.

Since the refractory metal cemented fused carbide of the present invention is a cemented phase of at least four reinforcing phase compounds with at least one refractory metal, the reinforced phase compound is combined with the refractory metal cement phase in a molten manner to form a refractory The metal cements the molten carbide, and in the following examples, the TiC having a melting point of about 3000 ° C and a hardness of more than 3000 HV and the refractory metal Mo having a melting point of more than 2600 0 C are used to prepare porcelain gold having different TiC and Mo contents; And adding other gap type VI, V, VI B group carbides: ZrC, HfC, VC, NbC, TaC, WC, and multi-addition to make a refractory metal cemented molten carbide.

As shown in Fig. 1, in this embodiment, a vacuum arc melting furnace is used to refine the alloy, wherein the total weight of the reinforcing phase compound powder and the metal bulk material is about 50 g, placed in a water-cooled copper mold 101, and covered. After the upper lid is closed and vacuumed to 2.4 x 10 ^-2 torr, pure argon gas is introduced to about 8.0 torr, and then vacuum is applied, and the process of purging is repeated three times before smelting 102. The smelting current is 550 amps. After the smelting is completed, it is completely cooled. Then the alloy block is turned over and smelted. The total amount will be repeated for more than four times to ensure that all the porcelain gold elements are uniformly mixed in the test piece, and finally destroyed after complete cooling. The ingot was taken out under vacuum, and this was a cast test piece 103.

Since the analysis will be carried out with 7 sets of porcelain gold in this embodiment, the gold code and composition of the 7 sets of porcelain gold are as shown in Fig. 2, and the 7 sets of porcelain gold components (at %) are as shown in Fig. 3. The weight ratio (wt%) of the porcelain gold component shown in Fig. 4, the volume ratio (vol%) of the porcelain gold component, and the overall density (g/cc) are shown in Fig. 5, and the components are well matched. Thereafter, the alloy is refined through the vacuum arc melting furnace, and the as-cast test piece is subjected to the following analysis: (1) preliminary microstructure observation and composition analysis of the surface by scanning electron microscope; (2) XRD diffractometer for X-ray diffraction measurement; (3) Using Vickers hardness to measure the overall hardness of porcelain gold; (4) Drying test for dry grinding without lubrication; (5) High temperature hardness tester The machine measures the high temperature hardness; (6) It is cut into the shape of a diamond turning tool using a lathe and polished for cutting test.

The microstructure analysis of 7 sets of porcelain gold was carried out and analyzed as follows: (1) Among them, C1M1 to C3M1 mainly contain diffraction peaks of two structures (MC type carbides of FCC structure (Metal: Carbide = 1:1) and BCC structure) Solid solution of Mo), C4M1 to C7M1 mainly contain three kinds of structural diffraction peaks (MC type carbide of FCC structure, Mo solid solution of BCC structure and M2C type carbide of Hexagonal (Metal : Carbide = 2 : 1) ). (2) It can be seen from Fig. 6A and Fig. 6B that the BEI images are 200 times and 1000 times of C1M1 porcelain gold, respectively. Among the C1M1 porcelain gold, the black phase is primary crystal TiC and some solid Mo is dissolved, and the layered total The crystal structure is composed of a solid solution of eutectic TiC and Mo; it is a typical dendritic and interdendritic crystal structure, the black phase is dendritic, and the white phase is interdendritic crystal structure. (3) The C1M1 porcelain gold ~ C7M1 porcelain gold has a dendrite and interdendritic crystal structure as a whole, and it can be seen from Fig. 7A to Fig. 7C that BEI of C4M1 porcelain gold is 200 times, 1000 times and 3000 times respectively. The image shows that the microstructure is obviously different from C1M1, C2M1 and C3M1; and it can be divided into main four phases by X-ray diffraction analysis and BEI metallographic structure: black phase, white phase, total The crystal structure and the largest feature of the porcelain gold "grey phase" are shown in the figure. The black phase is the same as the previous three systems, and is a primary MC type carbide ((Ti + Zr + Nb + V) : Carbon = 1 : 1), or (Ti, Zr, Nb, V) C and a small amount of solid solution. The solid solution of Mo, the layered eutectic structure is composed of eutectic MC type carbide and Mo-based solid solution; in addition, the layered eutectic structure of the porcelain gold layer is significantly less, resulting in more white phase, The white phase is a solid solution mainly composed of Mo. The gray phase is inferred to be a M2C type carbide ((Ti + Zr + Nb + V + Mo): Carbon = 2 : 1), which is formed by the transformation of a part of the inter-dendritic white phase. Unlike MC type carbides, M ₂ C type carbides have more solid solution Mo (about 46 at %), which is much larger than 17 at % of MC carbides. Therefore, it is speculated that the phase separation hardness of this phase is between Between the white phase of the MC carbide and the solid solution of the metal Mo, but since the phase separation is precipitated from the original interdendritic metal cement phase, the overall hardness is greatly improved. (4) While C4M1 porcelain gold ~ C7M1 porcelain gold has a micro-structure phenomenon similar to C4M1 porcelain gold, it can be seen that the Mo-based carbide porcelain gold system has a significant increase in hardness after multi-addition (C4M1 ~ C7M1), among which When added to VC, there will be a carbide of the M ₂ C type, and it is a dendritic crystal with the solid solution of the cement phase Mo.

Seven sets of porcelain gold were used to measure the overall hardness of porcelain gold. The results are shown in Fig. 8. The Hardness represents the overall hardness, K _IC represents toughness, and MC and M ₂ C are the phase separation hardness values, of which C1M1 ~ C3M1 The hardness rise is not obvious, and the phase separation hardness of C4M1 ~ C7M1 is about 1700 HV. Although the stronger phase MC carbide is soft, it is far harder than the cement phase Mo, which causes the C4M1~C7M1 system to increase its hardness. The C6M1 achieves the highest 1203 HV hardness value of the system.

Seven sets of porcelain gold were subjected to the abrasion test. The results are shown in Fig. 9A. As can be seen from the figure, the wear resistance (Wear Resistance) maintains a positive correlation with the MC carbide phase separation hardness value, as shown in Fig. 9B. The curve is further divided into three linear trend stages: (1) There is a sharp drop in impedance between C2M1 and C1M1 in the first stage, which is related to the sharp decrease in the phase hardness of MC carbide (the MC carbide of C2M1 is mainly the melting point). The high-hardness, softer ZrC precipitates first). (2) In the second stage, between C3M1 and C6M1, the wear resistance has a gradual upward trend, except that the phase separation hardness of MC carbide increases due to the multi-component addition, and is also related to the precipitation of M ₂ C carbide in the inter-dendritic crystal. (3) The decrease in the wear resistance of the last stage and the decrease in the phase hardness of the MC carbide between C6M1 and C7M1, and the decrease of the M ₂ C carbide in the inter-dendritic crystal due to the addition of the strong carbide former HfC related. It can be seen from the C4M1 system that the precipitation of M2C type carbides between the branches and the continuous phase increase of the phase-by-phase hardness of the strengthening phase MC carbides result in less local fracture density and less damage to the base phase scratches. Slightly, the overall wear resistance is greatly increased, and the wear resistance of the C6M1 is 31.26 m/mm3.

Seven sets of porcelain gold were measured for high temperature hardness. The results are shown in Fig. 10. As can be seen from the figure, the C1M1 to C7M1 porcelain gold system is heated from room temperature to 200 ̊C and gradually heated to 1000 ̊C. The hardness performance trend is a decrease in hardness with increasing temperature. Among them, C2M1 is the least, C6M1 is the most; C7M1 is the highest hardness at 1000 ̊C, about 850 HV, and C6M1 is from room temperature to 600 ̊C. The highest hardness is about 800 HV, but it is second at 1000 ̊C and about 800 HV.

Seven sets of porcelain gold were cut into the shape of a diamond turning tool using a lathe and polished to perform a cutting test. It was found that C6M1 performed relatively well in all the test pieces.

Based on the above, C6M1 porcelain gold is the Mo-based ceramic gold carbide reinforced phase multi-addition system, which has the best hardness, wear resistance performance, and good high temperature hardness and fracture toughness performance. Therefore, based on C6M1 porcelain gold, For this system, the variables of strengthening phase carbide and cement phase metal Mo are mainly used to strengthen the phase carbide. The variable method is to select the carbide with the highest hardness of each of the IV, V and VI B gap carbides. , increase its proportion, the C6M1 adjusted porcelain gold code and composition is shown in Figure 11, and the C6M1 adjusted porcelain gold composition (at %) is shown in Figure 12, the analysis is as follows: 1) Among them, C6M1Ti2, C6M1V2 and C6M1W2 are twice the ratio of TiC, VC and WC. After analysis, the hardness and toughness of C6M1W2 are significantly higher than that of C6M1 (although C6M1V2 hardness also rises) Less, but the toughness is slightly worse than C6M1W2) (2) Among them, C6M1W2, C6M1W3 and C6M1W4 are the ratio of TiC, VC and WC components to three or four parts. After analysis, C6M1W4 is compared with C6M1W3. There is a significant drop in toughness Phenomenon, and with the increase of WC content between dendrites have become less of Mo, but was replaced by M2C carbides trend, so there is toughness will gradually fall down phenomenon. (3) Among them, C6M1aW3Mo45, C6M1aW3Mo40, C6M1aW3Mo30 and C6M1aW3Mo55 are sequentially added to reduce the Mo content of C6M1W3 to 55, 45, 40, 30 at % of the porcelain gold code. After analysis, even if the Mo content of C6M1W3 porcelain gold is increased or decreased, Its microstructure is still composed of MC type carbide of FCC structure, M ₂ C carbide of Hexgonal structure and Mo solid solution of BCC structure; and with the decrease of Mo content, the overall performance will be like ceramic material. High hardness, but very easy to crack. (4) From the original (WC) ₃ , the article becomes (WC) _2.5 and (WC) _3.5 . For convenience of description, the same principle as (WC) _{3 is} referred to as C6M1W3, which will be (WC) _2.5 and (WC) _3.5 . The porcelain gold code is abbreviated as C6M1W2.5 and C6M1W3.5. Among them, the former Mo content also prepared 45 and 55 at % content C6M1'W2.5Mo45, C6M1'W2.5Mo55, after analysis, C6M1W2.5 and C6M1'W2. The biggest difference between 5Mo45 and C6M1'W2.5Mo55 porcelain gold is that C6M1W2.5 porcelain gold hardness is about 40 HV higher than C6M1W3, and the toughness is also maintained at 9.15 MPa‧m1/2.

The changes caused by the above-mentioned C6M1 porcelain gold-based variables are organized as follows: (1) Comparing the hardness and microstructure of C6M1 porcelain gold added with different WC content, it can be found that adding WC can increase the hardness of C6M1 porcelain gold to add The effect of 2.5 parts is the best, and the excessive addition promotes the formation of the eutectic structure, resulting in a decrease in the hardness of the porcelain gold. (2) The abrasion and wear tests of C6M1W2.5 and C6M1W3 with the best hardness and the second best, the damage of C6M1W2.5 and the scratch damage are slight, so the wear resistance is as high as 39.98 ± 1.62 m/mm3. The C6M1W3 also exhibits a higher impedance wear than the C6M1, 35.59 ± 1.43 m/mm3. (3) Decreasing the cement metal Mo, although the hardness will increase significantly, but the toughness will be greatly reduced. (4) It is concluded that the hardness and toughness can be better after the refractory metal cementation is added in a small amount, but it is not suitable for the multi-addition of the refractory metal cement phase.

The refractory metal cemented fused carbide provided by the present invention has the following advantages when compared with other conventional techniques: 1. The present invention melts a multi-component strengthening phase compound (four or more) and a finite element refractory metal cement phase ( At least one of combining and forming a refractory metal cemented fused carbide in a molten manner, combining the strengthening phase and the cemented phase, can overcome the problems of low density and high cost in the conventional sintering process, and can A composite material with high hardness, high melting point and high toughness is produced. 2. The refractory metal cemented fused carbide produced by the invention is a composite structure of coarse dendrites and inter-dendritic crystals, so it is opposite to the sub-micron scale structure pursued by the sintering process, but the overall process It is fast, convenient, and has a density of 100%, and a molten composite with good hardness and toughness. These advantages are comparable to or better than traditional sintered composite materials.

The present invention has been disclosed in the above embodiments, and is not intended to limit the present invention. Any of those skilled in the art can understand the foregoing technical features and embodiments of the present invention without departing from the invention. In the spirit and scope, the scope of patent protection of the present invention is subject to the definition of the claims attached to the present specification.

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[Fig. 1] is a schematic view showing the preparation process of the refractory metal cemented molten carbide of the present invention. [Fig. 2] is a schematic view showing the composition of the porcelain gold code and the porcelain gold of the refractory metal cemented fused carbide of the present invention. [Fig. 3] is a schematic view showing the gold composition of the refractory metal cemented molten carbide of the present invention. [Fig. 4] is a schematic view showing the weight ratio of the gold component of the refractory metal cemented molten carbide of the present invention. [Fig. 5] is a schematic view showing the volume ratio and overall density of the porcelain gold component of the refractory metal cemented molten carbide of the present invention. [Fig. 6A] is a 200-fold enlarged schematic view of a BEI image of C1M1 porcelain gold of the refractory metal cemented molten carbide of the present invention. [Fig. 6B] is a 1000-fold enlarged schematic view of a BEI image of C1M1 porcelain gold of the refractory metal cemented molten carbide of the present invention. [Fig. 7A] is a 200-fold enlarged schematic view of a BEI image of C4M1 porcelain gold of the refractory metal cemented molten carbide of the present invention. [Fig. 7B] is a 1000-fold enlarged schematic view of a BEI image of C4M1 porcelain gold of the refractory metal cemented molten carbide of the present invention. [Fig. 7C] is a 3000-fold enlarged schematic view of a BEI image of C4M1 porcelain gold of the refractory metal cemented molten carbide of the present invention. [Fig. 8] is a schematic view showing the overall hardness, toughness, and phase separation hardness values of C1M1 to C7M1 of the refractory metal cemented carbide of the present invention. [Fig. 9A] is a schematic view showing the overall hardness, the phase separation hardness value and the abrasion resistance of the C1M1 to C7M1 of the refractory metal cemented carbide of the present invention. [Fig. 9B] is a schematic diagram showing the trend between the MC phase separation hardness value and the abrasion resistance of the C1M1 to C7M1 of the refractory metal cemented carbide of the present invention. [Fig. 10] Fig. 10 is a schematic diagram showing the high-temperature hardness of C1M1 to C7M1 of the refractory metal-bonded molten carbide of the present invention at room temperature to 1273 K. [Fig. 11] is a schematic diagram showing the composition of the porcelain gold code and the porcelain gold of the C6M1 system of the refractory metal cemented molten carbide of the present invention. [Fig. 12] is a schematic diagram of the porcelain gold composition of the C6M1 system of the refractory metal cemented molten carbide of the present invention for strengthening the phase carbide and the binder phase metal.

Claims (4)

A refractory metal cemented fused carbide comprising: at least four reinforcing phase compounds and at least one refractory metal cement phase, wherein the reinforced phase compound and the refractory metal cement phase are combined in a molten manner to form a refractory Metal cemented carbides. The refractory metal cemented molten carbide according to claim 1, wherein the strengthening phase compound used is TiC, ZrC, NbC, VC, TaC, WC, HfC, TiN or ZrN, which is capable of being in the above-mentioned strengthening phase compound. At least four or more types are selected for fusion bonding with the refractory metal cement phase. The refractory metal cemented molten carbide according to claim 1, wherein the refractory metal cement phase used is Mo, W, Nb, Hf, Ta or Re, and at least one of the above refractory metal cemented phases can be selected. The strengthening phase compound is combined. The refractory metal cemented molten carbide according to claim 2 or 3, wherein the melting mode is vacuum arc melting at a temperature exceeding 3500 degrees Celsius, so that the prepared refractory metal cemented molten carbide is one having dendrites A composite structure with intergranular crystals.