JPS6122016B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing titanium carbide (TiC)-based cermets that have both excellent wear resistance and impact resistance. Traditionally, TiC-based cermets were originally TiC-Ni-Co.
system dominated, followed by TiC−TaC−WC−Ni−
Co-Mo based materials have become mainstream, and in recent years, the addition of new components such as TiN and TaN has been considered, and in this case, a content of around 20% will improve impact resistance. However, compared to tungsten carbide (WC)-based sintered cemented carbide, its impact resistance is still inferior to that of tungsten carbide (WC)-based sintered cemented carbide, and as a result, accidents due to breakage occur in practical use. Therefore, the biggest challenge for TiC-based cermets has always been to further improve their impact resistance. In this way, the history of development aimed at improving the properties of cermets has centered on composition, searching for new additives, and research focused on crystal grain size, particularly ultra-coarse crystals, as in this invention. I have never seen an example of this being done. This is because it is the main component of TiC-based cermets.
TiC has inferior sintering properties compared to tungsten carbide (WC), which is the main component of the cemented carbide alloy. Therefore, when manufacturing TiC-based cermets, it is necessary to crush the raw material powder to some extent. Not only is it difficult to make coarse-grained TiC-based cermets with a grain size of 4 to 6 μm, but fine-grained TiC-based cermets with an average grain size of 1 to 3 μm have higher resistance. Moreover, it has high impact resistance, and considering that many of the cut TiC-based cermets have a fine-grained structure, it is easy to understand that no research has focused on ultra-coarse-grained crystals. From the above-mentioned viewpoints, the present inventors have developed a material that combines the above-mentioned conventional TiC-based cermets with the aim of obtaining a material that has both excellent wear resistance and impact resistance, and exhibits excellent cutting properties especially when used for cutting. As a result of research focusing on the crystal structure of
TiC crystal: 1-30% by volume, average diameter: 3-10μ
When the binder phase pool of m is uniformly dispersed in the structure, impact resistance equal to or higher than that of ordinary TiC-based cermets without the ultra-coarse-grained TiC crystals and binder phase pool is obtained. In addition to this, it also has excellent wear resistance. Note that the binder phase pool refers to a granular binder phase dispersed in the tissue. (b) The reason for the improved wear resistance is that TiC is harder than WC, is chemically stable, and has excellent heat resistance. In general, the smaller the crystal grain size, the more activated it becomes, so fine grains cannot provide the chemical stability and heat resistance inherent to TiC, but ultra-coarse grains with an average grain size of 7 μm or more have less chemical stability. and ensure heat resistance. In addition to the above-mentioned characteristics, the ultra-coarse grained TiC has the characteristic that the amount of solid solution in the binder phase is small, so it exists in the sintered structure in a form close to the particle size of the starting raw material powder. Because of this, it is most suitable as an ultra-coarse grain. The reasons listed above can be cited. (c) The reason for the improvement in impact resistance is that the propagation of cracks is prevented by the binder phase pool uniformly distributed throughout the structure, and stress is relaxed, resulting in a marked improvement in fracture toughness. It is assumed that this is due to the fact that the (d) Part of the TiC component in the ultra-coarse-grained TiC crystals is expressed in the periodic table in a relative proportion of 2 to 50 mol% (therefore, the relative proportion of TiC is 50 to 98%). 4a, 5a, and 6a group metal carbides and nitrides, while retaining the excellent wear resistance provided by TiC.
Impact resistance will be further improved. We have obtained the knowledge shown above. Therefore, the present invention was made based on the above knowledge, and when manufacturing a TiC-based cermet, the average crystal grain size:
Coarse TiC crystals with a grain size of 7 μm or more, and one or more carbides and nitrides of TiC and metals of groups 4a, 5a, and 6a of the periodic table, also having an average grain size of 7 μm or more. Uniformly disperse one or both of the composite compound crystals (containing TiC: 50 to 98 mol%) with two or more components (hereinafter referred to as metal carbon/nitride) at a ratio of 1 to 30% by volume. In addition, the average diameter of the bonded phase is 3 to 10 μm.
This method is characterized by a method for producing a TiC-based cermet that has both excellent wear resistance and impact resistance by forming and uniformly dispersing it as a binder phase pool. Next, in the method for producing TiC-based cermet of the present invention, the content and average crystal grain size of ultra-coarse grains, the average diameter of the binder phase pool, and the amount of metal replacement with carbon/nitride are limited as described above. Explain why. (a) Content of ultra-coarse crystals If the content is less than 1% by volume, the desired excellent wear resistance cannot be secured;
If the content exceeds 1% by volume, the sinterability of the cermet will deteriorate, making it easier to form cavities and pores, leading to deterioration of impact resistance. It was set at ~30% by volume. (b) Average grain size of ultra-coarse crystals If the average grain size is less than 7 μm, TiC itself cannot fully demonstrate its excellent chemical stability and heat resistance, resulting in improved wear resistance. Since it would be difficult to measure the thickness, the lower limit was set at 7 μm. In addition, uniform dispersion of ultra-coarse grain crystals having an average grain size of 7 μm or more in the alloy structure is achieved by using coarse powder with an average grain size of 9 μm or more as the raw material powder and blending it as part of the raw material powder. This is possible by thoroughly mixing the entire raw material powder. Therefore, the average particle size of the raw material powder is 9
Below μm, the average grain size in the alloy structure is 7
Ultra-coarse crystals of μm or more cannot be secured. (c) Average diameter of the binder phase pool If the average diameter is less than 3 μm, crack propagation cannot be completely prevented, while if the average diameter exceeds 10 μm, the wear resistance will be significantly reduced. The average diameter was determined to be 3 to 10 μm. In addition, the average diameter uniformly distributed in the alloy structure:
A binder phase pool of 3 to 10 μm is made by blending the starting raw material powder into a predetermined composition, pulverizing and mixing it wet, and drying it to form a mixed powder, which is then added with PVA.
(polyvinyl alcohol), pyryl wax, stearic acid, paraffin, etc., and has an average particle size of 3 to 10 μm. After mixing without pulverization, it is press-formed into a compact, which is pre-sintered to form pores in the pre-sintered compact, and then this pre-sintered compact is When the material is sintered, the voids are filled with the binder phase forming component, thereby forming the voids. Furthermore, the reason why the amount of organic compound powder added was set at 3 to 8% by weight as described above is because if the amount added is less than 3% by weight, the binder phase pool existing in the alloy structure is too small. This is because it is not possible to secure the desired excellent impact resistance, and on the other hand, if the amount added exceeds 8% by weight, the binder phase pool becomes too large and the wear resistance decreases. It is. In addition, in the conventional powder metallurgy method, organic compounds are added during wet grinding and mixing of the blended powder, and as a result, they become finely dispersed in the mixed powder, so the calcination after pre-sintering is There are no pores in the aggregate. (d) Amount of metal replaced by carbon/nitride As mentioned above, when a composite compound crystal consisting of ultra-coarse-grained TiC crystals partially replaced with metal carbon/nitride is dispersed in the structure, TiC The impact resistance of the alloy is further improved while retaining the excellent wear resistance provided by the components, so that the composite may be used as needed, especially where increased impact resistance is required. Compound crystals are dispersed in the alloy structure, but if the proportion of metal carbon/nitride in the composite compound crystal is less than 2 mol%, no further improvement in impact resistance can be obtained; If it exceeds 50 mol%, the relative proportion of the TiC component will be less than 50 mol%, and the chemical stability and heat resistance provided by the TiC component will not be fully exhibited. Since it becomes difficult to secure the desired wear resistance, the substitution ratio of metal carbon/nitride in the composite compound crystal was set at 2 to 50 mol%. Next, the method for producing the TiC-based cermet of the present invention will be explained with reference to Examples. Example 1 When manufacturing a conventional TiC-based cermet (hereinafter referred to as conventional cermet) 1 having a component composition of 85% TiC - 5% Mo - 10% Ni (volume %), 30 capacitance, which is a part of the TiC component, was used. % is composed of ultra-coarse grained TiC crystals having an average grain size of 9 μm,
Further, in the TiC-based cermet of the present invention (hereinafter referred to as the cermet of the present invention) 1 in which a (Ni+Mo) pool with an average diameter of 3 μm was present, and in the conventional cermet 1 described above, TiC: 30% by volume was added and the average crystal grain size was 9 μm.
Comparative TiC-based cermet 1 (hereinafter referred to as comparative cermet) composed of ultra-coarse-grained TiC crystals having In cermets, part 30
Comparative cermet 3, which was composed of TiC crystals having an average grain size of 4 μm outside the scope of the present invention, and in which a (Ni+Mo) pool having an average grain size of 3 μm was present, was subjected to the following procedure. Each was manufactured at That is, first, TiC powder having an average particle size of 1.5 μm, Mo powder having an average particle size of 1.0 μm, and Ni powder having an average particle size of 2.5 μm are prepared as starting raw material powders, and the ratio of these raw material powders to 100% is first determined. 55%TiC-5%Mo-10% as part (70%)
TiC powder with an average particle size of 9 μm by mixing Ni (volume %) and wet pulverizing and mixing in a ball mill for 100 hours, then reducing the balls in the ball mill to 1/10: 30 volume % was added to make it 100% and mixed for 10 hours, and then 7% by weight of wood wax having an average particle size of 3 μm was added as an organic compound powder to form a binder phase into a (Ni+Mo) pool. The cermet 1 of the present invention was manufactured by dry mixing without pulverization, followed by press molding, preliminary sintering, and main sintering under the manufacturing conditions of ordinary powder metallurgy. Comparative cermet 1 was manufactured under the same conditions as those used for manufacturing cermet 1 of the present invention, except that the addition of wood wax and preliminary sintering were not performed, and comparative cermet 2 was manufactured using ultraviolet cermet as the raw material powder. Produced under the same conditions as in the production of Cermet 1 of the present invention, except that coarse TiC powder was not used, that is, the starting raw material powder was blended from the beginning to have the composition of Conventional Cermet 1. did. Furthermore, comparative cermet 3 has an average particle size of 9μ
Cermet 1 was manufactured under the same conditions as those applied to the manufacture of cermet 1 of the present invention, except that TiC powder having an average particle size of 5 μm was used instead of TiC powder having an average particle size of 5 μm. Cermet 1 of the present invention obtained as a result has higher CIS (Cemented Carbide Tool Association Standard) SNP432 than Comparative Cermets 1 to 3 and Conventional Cermet 1.
A cutting chip with a shape according to the following was manufactured, Work material: SNCM-8 (Hardness H _B : 220), Chip honing: 0.1 x 25°, Cutting speed: 200 m/min, Feed: 0.3 mm/rev, Depth of cut. : 1.5 mm, cutting time: 10 min, Continuous cutting tests were conducted under the conditions of , and the flank wear (flank wear width) and crater wear (rake face wear depth) of the cutting edge were measured. : SNCM-8 (Hardness H _B : 280), Chip honing: None, Cutting speed: 140m/min, Feed: 0.2mm/rev., Depth of cut: 2mm, Cutting time: 2min, Intermittent cutting test was conducted under the following conditions. It was measured how many of the six cutting edges (chips) had defects. These measurement results are shown in Table 1.
The table also shows the average grain size of TiC crystals and the average diameter of Ni pools.

[Table] As shown in Table 1, the cermet 1 of the present invention
While maintaining the same excellent impact resistance as Comparative Cermets 2 and 3, which do not contain ultra-coarse grained TiC crystals, they exhibit significantly better wear resistance than these Comparative Cermets. On the other hand, the comparative cermet, which has ultra-coarse grained TiC crystals but no (Ni+Mo) pool, exhibits excellent wear resistance, but has significantly inferior impact resistance.
Furthermore, the cermet 1 of the present invention is significantly superior to the conventional cermet 1 in both wear resistance and impact resistance. Example 2 52%TiC-20%TiN-10%WC-6%Mo-12%
When manufacturing conventional cermet 2 with a composition of Ni (volume %), the starting material powder is
A part of the TiC powder has an average grain size of 15 μm for forming coarse composite compound crystals, and TiC/
The composition was TaC/NbC/ZrC=90 mol%/6 mol%/3 mol%/1 mol% (Ti, Ta, Nb,
Zr) C powder: 10% by volume, and an average particle size of 6 μm as an organic compound powder to form pores in the preliminary sintered body to serve as a binder phase (Ni + Mo) pool during main sintering. The cermet 2 of the present invention was manufactured under the same operating conditions as the cermet 1 of the present invention in Example 1, except that 7% by weight (extra number) of paraffin was added and mixed. Next, continuous cutting tests and interrupted cutting tests were conducted on the cermet 2 of the present invention and the conventional cermet 2 under the same conditions as in Example 1, except that the feed rate in the interrupted cutting tests was 0.3 mm/rev. The cutting test results are shown in Table 2, which also shows the average crystal grain size of the ultra-coarse crystals uniformly dispersed in the structure and the average size of the (Ni+Mo) pool. As shown in Table 2, the cermet 2 of the present invention
It is clear that Cermet 2 exhibits superior cutting characteristics in both continuous cutting and interrupted cutting tests compared to conventional Cermet 2.

[Table] Example 3 62%TiC-10%TaC-10%WC-6%Mo-6%
When manufacturing conventional cermet 3 having a composition of Ni-6%Co (volume %), a portion of TiC powder, which is the starting raw material powder, was mixed with 1 volume % of the average particle size:
20μm, TiC/TiN/WC=70mol%/20
(Ti, W)CN with a composition of mol%/10 mol%
Organic compound powder with an average particle size of 10 μm for replacing with powder and forming a binder phase consisting of Ni, Co, and Mo into a binder phase pool
The cermet 3 of the present invention was produced under the same operating conditions as the cermet 1 of the present invention in Example 1, except that PVA: 7% by weight (external number) was added and mixed.
was manufactured. Next, cutting tests were conducted on the cermet 3 of the present invention and the conventional cermet 3 under the same conditions as in Example 1. The test results are shown in Table 3. As is clear from the results shown in Table 3,
In this embodiment as well, the cermet 3 of the present invention has superior wear resistance and impact resistance compared to the conventional cermet 3.

[Table] Example 4 When manufacturing conventional cermet 4 having the composition of 50% TiC - 27% TiN - 10% WC - 13% Co (volume %), a part of the TiC powder as the starting material powder was , ultra-coarse TiC powder with an average particle size of 15 μm: 10% by volume, also with an average particle size of 12 μm, and
Tic/HfN/VN=80 mol%/10 mol%/10 mol%
(Ti, Hf, V), CN powder: 5% by volume, and average particle size: 10 as an organic compound powder to form the binder phase in the Co pool.
Cermet 4 of the present invention was produced under the same operating conditions as those used for producing Cermet 1 of the present invention in Example 1, except that 8% by weight (as an external number) of paraffin having a diameter of .mu.m was added and mixed. Next, the resulting cermet 4 of the present invention
A cutting test was conducted on the conventional cermet 4 under the same conditions as in Example 1, and the results shown in Table 4 were obtained. As shown in Table 4, average grain size: 12μ
Coarse TiC crystal with m and also 10μm

[Table] As a coarse composite compound crystal with (Ti,
The cermet 4 of the present invention, in which the Hf, V) CN crystals are uniformly dispersed in the structure, and the binder phase pool having an average diameter of 10 μm is evenly dispersed, is more suitable for continuous cutting and interrupted cutting than the conventional cermet 4. Demonstrates excellent cutting performance in any cutting,
It is clear that it has excellent abrasion resistance and impact resistance. Example 5 40%Tic-30%TiN-10%WC-5TaC-5%Ni
- When manufacturing conventional cermet 5 with a composition of 10% Co (volume %), a part of the TiC powder that is the starting raw material powder was converted into ultra-coarse TiC powder with an average particle size of 20 μm: 5 volume% and average particle size for coarse composite compound crystal formation: 15 μm;
and TiC/NbN/ _Mo2C =55 mol%/40 mol%/
Ultra-coarse particles (Ti, Nb,
Mo) CN powder: Consists of 1% by volume, and is an organic compound powder for forming a binder phase consisting of Ni and Co into a binder phase pool. Average particle size: 10 μm
Cermet 5 of the present invention was produced under the same operating conditions as in Example 1 for producing Cermet 1 of the present invention, except that 8% by weight of PVA having the following were added and mixed. Next, cutting tests were conducted on the cermet 5 of the present invention and the conventional cermet 5 under the same conditions as in Example 1, and the results shown in Table 4 were obtained. As shown in Table 4, Example 5 showed the same results as Example 4, and the cermet 5 of the present invention
It is clear that compared to the conventional Cermet 5, it exhibits superior cutting performance and has excellent wear resistance and impact resistance. As mentioned above, the TiC-based cermet produced by the method of the present invention has superior wear resistance and impact resistance compared to conventional TiC-based cermets, so it is suitable for use in cutting tools. Not only is it suitable for use, but it also exhibits excellent performance when used for wear resistance.

Claims (1)

[Claims] 1. When producing titanium carbide-based cermets, by blending and mixing coarse TiC powder with an average particle size of 9 μm or more as part of the raw material powder, an average Ultra-coarse titanium carbide crystals with a crystal grain size of 7 μm or more are uniformly dispersed at a ratio of 1 to 30% by volume, and an additional 3 organic compound powders with an average grain size of 3 to 10 μm are added to the mixed powder. It is added at a ratio of ~8% by weight, mixed without pulverization, and the green compact formed from this is pre-sintered to form pores in the preliminary sintered body, and these pores are removed during main sintering. By filling the binder phase-forming components by binding, binder phase pools with an average diameter of 3 to 10 μm are uniformly dispersed in the alloy structure, thereby improving wear resistance and impact resistance. A method for producing a titanium carbide-based cermet characterized by: 2. When producing titanium carbide-based cermets, one of coarse titanium carbide and metal carbides and nitrides of groups 4a, 5b, and 6a of the periodic table with an average particle size of 9 μm or more is used as part of the raw material powder. By blending and mixing a seed or a composite compound powder (containing titanium carbide: 50 to 98 mol%) with two or more components, ultra-coarse grains with an average grain size of 7 μm or more can be created in the alloy structure. 1 grain of the above composite compound crystal
Disperse uniformly at a ratio of ~30% by volume, and then add organic compound powder with an average particle size of 3 to 10 μm to the mixed powder at a ratio of 3 to 8% by weight, and mix without pulverization. The green compact formed from this is pre-sintered to form pores in the preliminary sintered body, and the pores are filled with a binder phase forming component through main sintering, thereby forming the same alloy structure. inside,
A method for producing a titanium carbide-based cermet, characterized by uniformly dispersing a binder phase pool with an average diameter of 3 to 10 μm, thereby improving wear resistance and impact resistance. 3 When manufacturing titanium carbide-based cermets, as part of the raw material powder, particles with an average particle size of 9.
Coarse titanium carbide powder of μm or larger, and composite compound powder containing one or more components of titanium carbide and carbides and nitrides of metals in groups 4a, 5a, and 6a of the periodic table (however, titanium carbide :50～
By blending and mixing 98 mol%), the average crystal grain size is 7 μm in the alloy structure.
ultra-coarse titanium carbide crystals and the above-mentioned composite compound crystals are uniformly dispersed at a ratio of 1 to 30% by volume, and an organic compound powder with an average particle size of 3 to 10 μm is added to the mixed powder. It is added at a ratio of 3 to 8% by weight, mixed without pulverization, and the green compact formed from this is pre-sintered to form pores in the pre-sintered body. By filling the alloy with binder phase-forming components through main sintering, binder phase pools with an average diameter of 3 to 10 μm are uniformly dispersed in the alloy structure, thereby improving wear resistance and impact resistance. A method for producing a titanium carbide-based cermet, characterized by measuring the following.