JP7205845B1 - wear resistant material - Google Patents

Abstract

By making a composite material in which hard W compound coarse particles with a large grain size are combined with the matrix phase of the cemented carbide, the wear of the binding phase is suppressed and the hard phase is less likely to break than the conventional WC-based cemented carbide. To provide a wear resistant member that can be restrained. A cemented carbide matrix having a hard phase mainly composed of WC fine particles having a particle size of 0.5 to 20 μm and a binder phase containing at least one selected from the group consisting of Ni, Co, Fe and Cr; W compound coarse particles with a particle size of 50 to 200 μm are present as a dispersed phase therein, and the W compound coarse particles are composed of coarse particles mainly composed of WC and/or W2C. Element.

Description

The present invention relates to wear resistant members.

Cemented carbide is often used for members in contact with workpieces, such as containers and molds for crushing, mixing, compacting, etc. workpieces such as carbides, metals, and ceramics. However, when the workpiece is powder of a hard material such as ceramics, the members in contact with the workpiece are significantly worn. Such wear becomes more pronounced as the powder particles of the workpiece are larger. Therefore, in recent years, there has been a demand for improved wear resistance and longer life of cemented carbide members that come into contact with such workpieces.

In general, the wear resistance and service life of a cemented carbide member in contact with a workpiece are improved by increasing its hardness. Cemented carbide can be hardened by increasing the hard phase, which is mainly composed of high-hardness WC. becomes smaller and the fracture toughness decreases. Therefore, when the workpiece is powder with high hardness and collides with it with high energy, simply increasing the hardness of the cemented carbide member does not lead to a long life.

Patent Document 1 describes a wear-resistant member that is hard to wear when it comes into sliding contact with a hard member, in which WC hard particles with an average particle size of 10 to 150 μm are bonded by a joint (soft metal phase) made of Co or Ni. Suggested by the member. However, when the average grain size of the WC hard particles is large (110 μm) as in Example 2, the distance between the hard particles (mean free path) is large, so the soft metal phase portion also becomes large, and wear occurs from there. easier to progress. On the other hand, when the average particle size of the WC hard particles is small (16 μm) as in Example 1, not only the wear of the metal phase but also the breakage of the hard particles becomes significant, resulting in insufficient wear resistance. be.

Patent Document 2 describes AlB ₂ , Al ₄ C ₃ , AlN, Al ₂ O ₃ , AlMgB ₁₄ , B ₄ C, cubic boron nitride (cBN), hexagonal boron nitride (hBN), CrB ₂ , Cr ₃ C ₂ , _{Cr2O3 , HFB2} , HfC, HfN, Hf(C,N), _MoB2 , _Mo2B5 , Mo2C, MoS2, _MoSi2 , _NbB2 , NbC, NbN, Nb _{( C} , _N ), SiB4, _SiB6 , SiC _{, Si3N4} , _SiAlCB , _TaB2 , TaC, TaN, Ta( _C ,N), TiB2, TiC, TiN, Ti(C,N), VB2, VC, VN , _V ( _C ,N), WB, _WB2 , _W2B5 , WC, _W2C , WS2, ZrB2, ZrC, ZrN, Zr( _C , _N ), ZrO2, and mixtures and alloys thereof The coated particles having an average particle size of less than 50 μm, which form an intermediate layer having higher fracture toughness than the core material on the core material consisting of at least one of the first particles containing W or WC and Co Disclosed is a consolidated material contained in a matrix that includes a mixture with secondary particles. When this material is used as a cutting tool, WC is dispersed even in the matrix portion, so it is less likely to wear during sliding. However, when the workpiece is a powder with high hardness and collides with high energy. It cannot be said that the wear resistance is sufficient. Further, in Patent Document 2, the core material is coated with a high-toughness material by various methods, but it cannot be said that sufficient wear resistance can be exhibited.

WO 2020/194628 A1 Patent No. 6257896

Accordingly, an object of the present invention is to produce a composite material in which hard W compound coarse particles having a large grain size are bonded by the matrix phase of a cemented carbide, thereby reducing the wear of the bonding phase more than the conventional WC-based cemented carbide. To provide a wear-resistant member capable of restraining and suppressing breakage of a hard phase. Such wear-resistant members are suitable for applications such as tools for kneading, injection, and compaction of hard powders such as ceramics, pulverizing blades, and tools for urban civil engineering.

In order to suppress the wear of the binder phase and the destruction of the hard phase, the present inventors considered using a W compound powder as the hard phase, which has a particle size that is somewhat larger than the powder particle size of the workpiece. rice field.

As the raw material W compound powder, a powder containing WC, W ₂ C, etc., having a fine structure, a hardness of 2500 HV, which is harder than WC, and a powder particle size of 100 μm was used. This W compound is hereinafter referred to as WC/W ₂ C. Using this powder, a mixed powder of WC/W ₂ C-3Cr-27Ni was produced, and after compaction, sintering was performed at 1200° C.-25 MPa by a hot press sintering method. This alloy showed high wear resistance against hard ceramic powder. However, when the wear surface was observed, it was found that the distance between the hard phase particles increased and the Ni-Cr phase, the matrix phase, was preferentially worn.

Therefore, the present inventors have found that if a cemented carbide using WC with a small particle size is used as a matrix phase and W compound hard particles with a relatively large particle size are dispersed, the wear of the matrix phase can be suppressed and the hard particles can be destroyed. can be suppressed, and high wear resistance can be exhibited against contact with ceramic powder having high collision energy, and the inventors have arrived at the present invention.

That is, the wear-resistant member according to one embodiment of the present invention comprises a hard phase mainly composed of WC fine particles having a particle size of 0.5 to 20 μm and at least one selected from the group consisting of Ni, Co, Fe and Cr. A cemented carbide having a binder phase containing a binder phase component is used as a matrix, and WC/W ₂ C coarse particles having a particle size of 50 to 200 μm and mainly composed of WC and W ₂ C are dispersed in the matrix. The WC/W ₂ C coarse particles have a lamellar structure of WC and W ₂ C, and at least part of the WC/W ₂ C coarse particles have a central portion and the binder phase component and an intermediate portion located between the central portion and the outer peripheral portion and containing more of the binder phase component than the outer peripheral portion, wherein the dispersed phase is 10 to 70 volumes % is included .

The W compound coarse particles preferably have a hardness higher than that of the WC fine particles.

The average particle size of the W compound coarse particles is preferably 5 to 70 times the average particle size of the WC fine particles.

Preferably, the binder phase is contained in an amount of 10-85% by weight relative to the matrix.

It is preferable that the WC fine particles have a Vickers hardness of 1700 to 2000 HV, and the W compound coarse particles have a Vickers hardness of 2000 to 3100 HV.

The WC/W ₂ C particles preferably have an atomic ratio of C to W of more than 0.5 and 0.9 or less.

It is preferable that the W compound coarse particles having the three-layer structure are contained in 30% or more of the entire W compound coarse particles.

According to the present invention, by dispersing W compound particles having a relatively large particle size in the matrix phase of a cemented carbide using WC having a small particle size as the hard phase, the wear of the matrix phase is suppressed and the hard phase is hardened. It can suppress breakage and falling off, and exhibits high wear resistance against contact with ceramic powder with high collision energy. For example, it is suitable for use as a tool for kneading, injecting, and compacting ceramic powder, crushing blades, and tools for urban civil engineering.

1 is an SEM photograph showing an example of a cross-sectional SEM structure of a wear resistant member of the present invention. FIG. 3 is a schematic diagram showing WC/W ₂ C coarse particles having a three-layer structure. 4 is a Ni mapping image showing an example of EDS analysis results of the wear resistant member of the present invention.

The wear-resistant member of the present invention has a hard phase mainly composed of WC fine particles having a particle size of 0.5 to 20 μm, and a binder phase containing at least one selected from the group consisting of Ni, Co, Fe and Cr. Cemented carbide is used as a matrix, and W compound coarse particles with a particle size of 50 to ₂₀₀ μm are present as a dispersed phase in the matrix. It is characterized by comprising particles.

The particle size of the hard phase WC fine particles is in the range of 0.5 to 20 μm. The particle diameter of the WC fine particles is the diameter of the WC fine particles in an arbitrary cross section of the super wear-resistant member converted to a circle with the same area. If the particle diameter of the WC fine particles exceeds 20 μm, the transverse rupture strength is lowered, and thicker portions of the binder phase increase, and wear tends to progress from there. If the grain size of the WC fine particles is less than 0.5 µm, they are likely to come off, and sufficient toughness cannot be obtained, resulting in reduced chipping resistance. The particle size of the WC fine particles is preferably in the range of 0.5-20 μm, more preferably in the range of 2-10 μm.

The binder phase contains at least one binder phase component selected from the group consisting of Ni, Co, Fe and Cr, and is preferably a metallic phase containing Ni and/or Co. The matrix is formed of a cemented carbide in which a hard phase containing WC fine particles as a main component is bound by a binding phase.

The binder phase content is preferably between 10 and 85% by weight of the total cemented carbide matrix. Here, the content of the binder phase means the total sum of the components added as binder phase components in the binder phase, and the components dissolved after being added as other components are not included in the content of the binder phase. . If the content of the binder phase is less than 10% by mass, the hardness of the cemented carbide becomes too high and the toughness decreases. Also, when the content of the binder phase exceeds 85% by mass, the number of thick portions of the binder phase increases. More preferably, the content of the binder phase is 10-85% by weight, more preferably 20-60% by weight, of the entire cemented carbide matrix.

The W compound coarse particles of the dispersed phase consist of coarse particles composed mainly of WC and/or _W2C . Coarse particles mainly composed of WC and/or W ₂ C are WC coarse particles mainly composed of WC, W ₂ C coarse particles mainly composed of W ₂ C, WC and W ₂ Contains WC/W ₂ C coarse particles composed mainly of C. WC/ _W2C coarse particles are composed of WC and W2C mixtures and contain _both WC and W2C _phases . _The WC/W2C coarse particles may partially contain eutectic of WC and _W2C . Here, "composed as a main component" means that each coarse particle may further contain a small amount of W, and may also contain W lower carbides containing binder phase components mixed in during the sintering process. do. By dispersing W compound coarse particles composed mainly of WC and/or _W2C in the cemented carbide matrix, it is possible to suppress the wear of the binder phase of the cemented carbide and suppress the fracture of the hard phase. The wear-resistant member of the present invention has excellent wear resistance even when the workpiece is a powder of high hardness and collides with high energy, such as when kneading, injecting, or compacting hard ceramic powder. can be demonstrated.

The W compound coarse particles constituting the dispersed phase preferably have a hardness higher than that of the WC fine particles. Wear of the binder phase of the cemented carbide is suppressed by allowing W compound coarse particles, which have a hardness greater than that of the WC fine particles and a larger particle size than the WC particles, to exist as a dispersed phase in the matrix of the cemented carbide. and suppresses the destruction of the hard phase, and the wear-resistant member of the present invention can obtain excellent wear resistance. It is more preferable that the W compound coarse particles have a hardness higher than that of the WC fine particles. The hardness of the WC fine particles is preferably 1700 to 2000 HV, more preferably 1700 to 1900 HV in terms of Vickers hardness. The W compound coarse particles preferably have a Vickers hardness of 2000 to 3100 HV, more preferably 2400 to 3100 HV. The W compound coarse particles preferably have a Vickers hardness of 100 HV or higher, more preferably 200 HV or higher, and particularly preferably 300 HV or higher than the WC fine particles. The Vickers hardness of the WC fine particles and the W compound coarse particles may be determined by Vickers hardness test on a test piece of the same material, or may be measured by nanoindentation and converted to Vickers hardness. Alternatively, the hardness of WC fine particles may be the literature value (Hisashi Suzuki, ed.: Cemented Carbide and Sintered Hard Materials - Fundamentals and Applications -, p2).

In particular, when WC coarse particles are used as the W compound coarse particles, the Vickers hardness of the WC coarse particles is preferably 2000 to 2400 HV, and the WC coarse particles have a Vickers hardness of 100 HV or more than the WC fine particles. It is preferable to have Combining WC fine particles with low Vickers hardness and coarse WC particles with high Vickers hardness in this way suppresses the wear of the cemented carbide binder phase and the destruction of the hard phase, resulting in excellent wear resistance. You can get sex. In addition, since WC coarse particles do not contain a W ₂ C phase, they are inferior in hardness to WC/W ₂ C coarse particles, but are excellent in the balance between hardness and toughness. WC coarse particles having a high Vickers hardness may be produced by increasing the hardness of commercially available WC particles by heat treatment.

The particle size of the W compound coarse particles in the dispersed phase is within the range of 50 to 200 μm. The particle size of the W compound coarse particles is obtained by the same method as for the particle size of the WC fine particles. If the grain size of the W compound coarse particles is less than 50 μm, the hard phase may be detached or broken, resulting in insufficient wear resistance. On the other hand, if the grain size of the W compound coarse particles exceeds 200 μm, the workpiece may be damaged, and the partial mean free path of the binder phase becomes large, resulting in abrasion of the binder phase. The grain size of the W compound coarse particles is preferably in the range of 50-200 μm, more preferably in the range of 110-180 μm.

The average particle diameter of the W compound coarse particles in the dispersed phase is preferably 5 to 70 times the average particle diameter of the WC fine particles in the hard phase. The average particle diameter of WC fine particles is obtained by dividing the sum of the areas of all WC fine particles in an arbitrary cross section of the wear-resistant member by the number of WC fine particles, and dividing the average area per WC fine particle by the diameter of a circle with the same area. converted to . The average particle size of the W compound coarse particles is also obtained by the same method as for the average particle size of the WC fine particles. When the average particle diameter of the W compound coarse particles relative to the average particle diameter of the WC fine particles is within this range, the wear-resistant member of the present invention can obtain high hardness and high fracture toughness in a well-balanced manner. It can exhibit better wear resistance when the object is powder with high hardness and collides with high energy. The average particle diameter of the W compound coarse particles in the dispersed phase is more preferably 5 to 70 times, more preferably 10 to 40 times, the average particle diameter of the WC fine particles in the hard phase.

The content of the dispersed phase is preferably 10-70% by volume with respect to the entire wear-resistant member. Here, the content of the dispersed phase means the total sum of the components added as dispersed phase components in the dispersed phase, and the components that are dissolved after being added as other components are not included in the content of the dispersed phase. . If the content of the dispersed phase is less than 10% by volume, the hardness of the wear-resistant member is poor and the wear resistance is insufficient. On the other hand, when the content of the dispersed phase exceeds 70% by volume, the hardness of the wear-resistant member becomes too high, resulting in a decrease in toughness. The content of the dispersed phase is more preferably 20-70% by volume, more preferably 30-65% by volume, relative to the entire wear-resistant member.

The W compound coarse particles dispersed in the cemented carbide matrix preferably consist of WC/W ₂ C coarse particles. WC/W ₂ C coarse particles easily obtain a fine two-phase structure, so they have sufficient hardness and are excellent in wear resistance and impact resistance. Therefore, by allowing the WC/W ₂ C coarse particles having a larger particle size than the WC fine particles in the cemented carbide matrix to exist as a dispersed phase in the cemented carbide matrix, the wear-resistant member of the present invention is excellent. It can exhibit wear resistance and impact resistance, and can be suitably used when the workpiece is powder with high hardness and collides with high energy. It is particularly preferable that the WC/W ₂ C coarse particles have an atomic ratio of C to W of more than 0.5 and 0.9 or less.

_The WC/W2C coarse particles preferably have a lamellar structure of WC and _W2C . The lamellar structure of WC and W ₂ C means a structure in which WC phases and W ₂ C phases are alternately formed in layers. Here, FIG. 1 shows an example of a cross-sectional SEM structure of the wear resistant member of the present invention. As shown in FIG. 1, the WC/W ₂ C coarse particles in the cross-sectional SEM structure of the wear-resistant member have a lamellar structure in which WC phases and W ₂ C phases are alternately formed in layers, especially in the central part. ing. By forming such a lamellar structure with an extremely thin phase, the WC/W ₂ C coarse particles have high hardness, and at the time of wear, fine local fractures progress little by little, which reduces the wear rate. The WC/W ₂ C coarse particles, which are slow and have a lamellar structure of WC and W ₂ C, can impart particularly excellent wear resistance and impact resistance to the wear resistant member of the present invention.

At least part of the WC/W ₂ C coarse particles are located between the central portion 1, the outer peripheral portion 2 slightly containing the binder phase component, and the central portion 1 and the outer peripheral portion 2, as shown in FIG. It preferably has a three-layer construction with a middle portion 3 containing more binder phase components than the outer portion 2 . This is because the WC/W ₂ C coarse particles were added as a dispersed phase to the cemented carbide matrix and sintered, so that the binder phase components and carbon diffused and penetrated from the matrix to the WC/W ₂ C coarse particles. WC is formed in the outer peripheral portion 2, and as it cools, the binder phase component of the liquid phase in the outer peripheral portion 2 moves to the intermediate portion 3 and solidifies and shrinks according to the solidification of the intermediate portion 3, which has a high solidification temperature. As a result, it is considered that the binder phase component in the intermediate portion 3 is the largest. As a result, lower carbides containing binder phase components such as Me ₃ W ₃ C (Me is a binder phase component) are formed in the intermediate portion 3 of the WC/W ₂ C coarse particles, and they are compared with WC and W ₂ C. Since the coefficient of thermal expansion is large, the amount of contraction is greater than that of other portions during cooling due to the presence of the intermediate portion 3 containing a large amount of lower carbides inside, and as a result, the surface portion of the WC/W ₂ C coarse particles is subjected to compressive stress. , and the WC/W ₂ C coarse particles having such a three-layer structure can impart extremely excellent wear resistance and impact resistance to the wear resistant member of the present invention.

FIG. 3 shows a Ni mapping image of an example of EDS analysis results of the wear-resistant member of the present invention using WC/W ₂ C coarse particles as a dispersed phase in a WC-Ni-Cr alloy matrix. show. As shown in FIG. 3, the outer peripheral portion 2 contains Ni, which is the binder phase component of the WC/W ₂ C coarse particles, and the intermediate portion 3 contains more Ni, which is the binder phase component, than the outer peripheral portion 2. I know you are.

If at least some of the WC/W ₂ C coarse particles have a three-layer structure, the above effect can be obtained, but 30% or more of the total number of W compound coarse particles has a three-layer structure ₂ C coarse particles are preferable, and 50% or more of the particles are preferably WC/W ₂ C coarse particles having a three-layer structure. In addition, it is desirable that 90% or more of the W compound coarse particles having a particle size equal to or larger than the average particle size of the W compound coarse particles are WC/W ₂ C coarse particles having a three-layer structure, and 95% or more are three-layer WC/W ₂ C coarse particles having a structure are more desirable. As a result, even better wear resistance and impact resistance can be imparted to the wear resistant member of the present invention.

The wear resistant member of the present invention can be produced by the following method. Powders of each component constituting the matrix phase are prepared and mixed by a wet ball mill or the like to prepare a mixed powder. to prepare. By sintering this raw material powder, the wear resistant member of the present invention is obtained. A hot press sintering method is preferably used as the sintering method. The sintering method is not limited to the hot press sintering method, and any known sintering method can be used as appropriate.

The present invention will be explained in more detail by examples, but the present invention is not limited to them.

Example 1
WC/W ₂ C powder (particle size 20-300 μm) and WC powder (particle size 110 μm) were used as the dispersed phase, and WC powder (particle size 0.3-18 μm) and Cr ₃ C ₂ powder were used as the matrix phase. (particle size 2 μm), Cr powder (particle size 30 μm), Co powder (particle size 1.5 μm), Ni powder (particle size 2.8 μm), Fe powder (particle size 3 μm) and (Ta, Nb) C powder (particle size 2 μm) was used. The WC/W ₂ C powder used had an atomic ratio C/W of C to W of 0.64 and had a lamellar structure of WC and W ₂ C.

The powders shown in Table 1, which constitute the matrix phase, were mixed by a wet ball mill to prepare a mixed powder. WC powder having the particle size shown in Table 2 was used. Invention products 6 and 11 have Cr added, and invention products 2, 5 and 8 have VC, (Ta,Nb)C and Mo added, respectively. WC/W ₂ C powder having a predetermined amount and particle size shown in Table 2 was added to the obtained mixed powder and mixed (only Invention 11 used WC powder instead of WC/W ₂ C powder). , to prepare raw material powders. The raw material powder was sintered by a hot press sintering method at a sintering temperature of 1100-1300° C. and a pressure of 20-50 MPa to obtain wear-resistant members of Inventive Products 1-12 and Comparative Products 1-5.

The Vickers hardness of the wear resistant members of Invention Products 1 to 12 and Comparative Products 1 to 5 was determined. The Vickers hardness was measured using a Vickers hardness tester HV30, and the transverse rupture strength was measured by a three-point bending test based on JISR 1601. SEM images (observation magnification: 1,000 times) of the polished cross sections of the wear-resistant members of Invention Products 1 to 12 and Comparative Products 1 to 5 were taken, and the presence or absence of a three-layer structure of W compound coarse particles was confirmed by EDS. The wear resistance of the wear-resistant members of invention products 1 to 12 and comparative products 1 to 5 was evaluated by the amount of wear after pressing the samples against the end face of the disk of the mating member in ceramic abrasive grains for a certain period of time. Table 3 shows the results obtained.

Inventive products 1 to 9 and 12 were excellent in sinterability, had almost no dropout or breakage of WC particles, and had good wear resistance. Inventive product 11 uses WC coarse particles as W compound coarse particles, and the WC particles hardly fall off or break, and the abrasion resistance is sufficient. Comparative product 1 contained few W compound coarse particles, so WC particles in the matrix phase were likely to fall off, and sufficient wear resistance could not be obtained. Since the W compound coarse particles of Comparative Product 2 had a small particle size, they easily fell off, and sufficient wear resistance was not obtained. In Comparative Product 3, the WC particles in the matrix phase were too small in diameter, so they tended to come off, and the abrasion resistance was not sufficient. Comparative product 4 was not usable because the grain size of the W compound coarse particles was too large, and the mating material was sometimes damaged. Comparative product 5 had an excessively large volume fraction of W compound coarse particles, and therefore had slightly inferior sinterability and low wear resistance. In addition, since Invention 10 has a large amount of binder phase in the matrix phase, W compound coarse particles formed by compounds of binder phase components (particularly Ni) can be seen in the outer periphery of coarse particles of the dispersed phase, and the wear resistance is somewhat low. inferior.

Claims (7)

A cemented carbide having a hard phase mainly composed of WC fine particles having a particle size of 0.5 to 20 μm and a binder phase containing at least one binder phase component selected from the group consisting of Ni, Co, Fe and Cr. WC/W ₂ C coarse particles composed mainly of WC and W ₂ C having a particle size of 50 to 200 μm are present as a dispersed phase in the matrix,
The WC/W ₂ C coarse particles have a lamellar structure of WC and W ₂ C,
At least part of the WC/W ₂ C coarse particles are located between a central portion, an outer peripheral portion containing the binder phase component, and between the central portion and the outer peripheral portion, and the binder phase component has a three-layer structure comprising a middle portion containing a large amount of
A wear-resistant member characterized by containing 10 to 70% by volume of the dispersed phase . _2. The wear resistant member according to claim 1, wherein said WC/W2C coarse particles have a hardness higher than that of said WC fine particles. 2. The wear-resistant member according to claim 1, wherein the average particle diameter of said WC/W ₂ C coarse particles is 5 to 70 times the average particle diameter of said WC fine particles. 4. The wear resistant member according to any one of claims 1 to 3, wherein the binder phase is contained in an amount of 10 to 85% by mass with respect to the matrix. 5. The method according to any one of claims 1 to 4 , wherein the WC fine particles have a Vickers hardness of 1700 to 2000 HV, and the WC/W ₂ C coarse particles have a Vickers hardness of 2000 to 3100 HV. The wear resistant member according to . 6. The wear resistant member according to claim 1 , wherein the WC/W ₂ C coarse particles have an atomic ratio of C to W of more than 0.5 and not more than 0.9. The wear resistant material according to any one of claims 1 to 6 , wherein 30% or more of the WC/W 2 _C coarse particles having the three-layer structure are included in the entirety of the WC/W ₂ C coarse particles. Element.

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