JPS633017B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cermet that has high hardness and high toughness, and exhibits excellent wear resistance and impact resistance particularly when used as a cutting tool. [Conventional technology] Conventionally, titanium carbide (hereinafter referred to as TiC) is generally used.
TiC-based cermets, whose main component is containing titanium nitride (hereinafter referred to as TiN).
TiC-based cermets are attracting attention. [Problems to be solved by the invention] However, when this TiN-containing TiC-based cermet has a high TiN content, when it is vacuum sintered, the TiN decomposes during sintering, and the decomposed nitrogen is released into the pores. Because these particles remain in the cermet and the desired toughness cannot be improved, at most
10 to 25% by weight (hereinafter weight% is simply expressed as %)
It is only possible to contain TiN, and this
A TiN content of about 10 to 25% cannot sufficiently improve toughness. Therefore, TiN
Multiple TiN with content exceeding 25% by weight
When manufacturing cermets containing TiN, sintering in a nitrogen atmosphere is being considered in order to suppress the decomposition of TiN, but cermets containing a large amount of TiN have extremely poor sinterability. It has the disadvantage that it is difficult to produce a dense, high-strength cermet, so it is currently hardly ever put into practical use. [Means for Solving the Problems] Therefore, the inventors of the present invention have conducted various studies in order to obtain a cermet with a TiN content of over 25%, which is also dense and has high strength. Cermets are difficult to form a cored structure with TiC as a core, which is seen in conventional TiC-based cermets, and in particular, the peripheral structure surrounding the core is unevenly developed; Mo or Mo ₂ C, which was an essential component to improve the wettability with the binder phase, does not enter the surrounding tissue when added to a cermet with a high TiN content, improving the wettability with the binder phase. It was found that it did not show any effect, but rather inhibited sinterability. Therefore, we made various prototype cermets with a high TiN content that did not contain any Mo or Mo ₂ C, which were considered essential components in conventional TiC-based cermets, and found that tungsten carbide (hereinafter referred to as WC) and Ta , Nb and Zr carbides (hereinafter referred to as TaC, NbC and ZrC)
In cermets containing one or more of the following (hereinafter collectively referred to as metal carbides), the metal carbide and WC are
TiC forms a surrounding structure together with TiC and TiN.
, and stabilizes the surrounding structure to improve its sinterability, while Co is optimal as the binder phase component, and a part of Co can be replaced by Ni (however, Co>Ni) There was found. This invention was invented based on the above knowledge, and includes TiN: 25 to 45%, TiC: 15 to 35%, WC: 10 to 30%, metal carbide: 5 to 25%, Co or Co. and Ni (where Co>Ni): 7.5 to 25%, and the hard dispersed phase is TiC
is the core, and the surrounding area is made of metal carbide, WC, TiC.
It has a two-phase structure consisting of a NaCl-type solid solution phase with a core structure surrounded by a solid solution consisting of TiN and TiN, and a titanium nitride phase, while the binder phase is Co or Co in which W and Ti are dissolved in solid solution.
The present invention relates to a cermet for cutting tools characterized by having a structure consisting of Ni and Ni. Next, in this invention, the reason why the structure range of each component constituting the cermet is limited as described above will be explained. (a) TiN TiN is a solid solution in the periphery of the cored structure,
It is divided into those that are dispersed alone as a TiN phase, and those that are dispersed as a TiN phase.
Both have the effect of suppressing grain growth of the dispersed phase,
It has the effect of improving the impact resistance of cermets, but if the TiN content is less than 25%, there will be no TiN phase in the cermets, and as a result, the toughness and wear resistance of cermets will be lower than those with TiN phases. and become inferior, while 45%
If the content exceeds 25%, decomposition will occur during sintering, leaving pores in the cermet and significantly deteriorating the toughness of the cermet. Therefore, the content was set at 25 to 45%. (b) TiC Since TiC itself has high hardness, it has the effect of improving the wear resistance of cermets, but if the content is less than 15%, the relative
The proportion of the NaCl-type solid solution phase is too small to ensure the desired excellent wear resistance;
If the content exceeds 35%, the toughness of the cermet decreases, so the content was set at 10 to 35%. (c) WC WC has the effect of stabilizing the formation of surrounding structures by dissolving in the NaCl-type solid solution phase, thereby improving the toughness of cermets.
If it is less than 10%, the desired stabilizing effect cannot be obtained;
On the other hand, if the content exceeds 30%, the WC phase will be present in the hard dispersed phase and the wear resistance of the cermet will decrease, so the content was set at 10 to 30%. (d) TaC, NbC, and ZrC These components, together with WC, dissolve in the NaCl-type solid solution phase to stabilize the formation of the surrounding structure and improve the toughness of the cermet, as well as its plastic deformation resistance. However, if the content is less than 5%, the desired effect of improving the above effect cannot be obtained, while if the content exceeds 25%, the wear resistance of the cermet will decrease. The content was set at 5-25%. (e) Co or Co and Ni These components have the effect of forming a binder phase in the cermet and improving the toughness of the cermet, but if their content is less than 7.5%, the desired excellent toughness cannot be achieved. while 25% cannot
If it is contained in excess of If Ni is not less than the amount of Co, the desired excellent toughness cannot be secured, so the content of these is set at 7.5 to 25%, and when Ni is used in combination with Co, the amount of Co is The amount was determined to be higher than the amount of Ni. The cermet of the present invention is preferably obtained by pressing a mixed powder obtained by mixing the metal powder or chemical powder to the above composition at a pressure of 10 to 30 kg/mm ² to form a green compact. is 1Torr
It is manufactured by sintering at a temperature of 1400-1550°C in a nitrogen atmosphere. [Example] Next, the present invention will be explained by referring to an example. Example 1 Raw material powder has an average particle size of 1.5 μm
TiN powder, 2.0μm TiC powder, 1.0μm TaC
powder, 1.4μm NbC powder, 2.2μm ZrC powder,
Same 0.8μm WC powder, same 1.2μm Co powder and same
2.5 μm Ni powder was prepared, each of these raw material powders was blended into a predetermined composition, wet pulverized and mixed in a ball mill for 72 hours, dried, and then press-molded into a green compact at a pressure of 15 kg/mm ² . , and then by sintering under the conditions shown in Table 1, the first
Cermets of the present invention having the compositions shown in the table 1-
No. 15 and comparative cermets 1-8 were prepared, respectively. It should be noted that Comparative Cermets 1 to 8 were all tested under conditions in which one of the compositional components (those marked with * in Table 1) was outside the scope of the present invention. Next, the structures of the cermets 1 to 15 of the present invention and comparative cermets 1 to 8 thus obtained were observed.
8, the hard dispersed phase is a NaCl type solid solution phase.
Although it has a two-phase structure with a TiN phase, the TiN content is low and outside the scope of this invention, and the TiC
There was no TiN phase in Comparative Cermet 1, whose WC content was higher than the range of this invention, and a WC phase was present in Comparative Cermet 6, whose WC content was higher than the range of this invention. . Furthermore, for the present invention cermets 1 to 15 and comparative cermets 1 to 8, transverse rupture strength was measured for the purpose of evaluating pore generation status (ASTM standard), Rockwell hardness (A scale), and toughness, and the work material : JIS/SNCM-8 (Hardness: H _B 240), Cutting speed: 200m/min., Feed: 0.36mm/rev., Depth of cut: 2mm, Cutting time: 10min., Continuous cutting of steel round bar under the following conditions. Test and work material: JIS/SNCM-8 (Hardness: H _B 270), Cutting speed: 140m/min., Feed: 0.3mm/rev., Depth of cut: 2.5mm, Cutting time: 3min., Conditions: In the above continuous cutting test, the flank wear width and rake face wear depth of the cutting edge were measured. The number of blades was measured. The results of these measurements are shown in Table 2. Table 2 also shows commercially available TiC-based cermets (conventional cermet 1) and TiN: 15% for comparison purposes.
The cutting test results of a TiC-based cermet (conventional cermet 2) containing TiC under the same conditions are also shown. From the above results, the present invention cermets 1 to 15 all have high hardness and high toughness, and show excellent wear resistance and impact resistance in the cutting test, whereas the comparative cermets 1 to 8 and the conventional cermets 1-2
The cermets were inferior in at least one of these properties, and all of them were inferior except for comparative cermet 8, in which the content of bonding metal was higher than the range of the present invention. intermittent

【table】

〔Effect of the invention〕

As is clear from the above description, the cermet of the present invention has high hardness and high toughness, and when used as a cutting tool material, exhibits extremely excellent wear resistance and impact resistance. be.

Claims (1)

[Claims] 1 Titanium nitride: 25 to 45%, Titanium carbide: 15 to 35%, Tungsten carbide: 10 to 30%, one or two of Ta, Nb, and Zr carbides.
It has a composition (by weight) consisting of: 5% to 25% Co or Co or Co and Ni (Co > Ni), and the hard dispersed phase has a core of titanium carbide and Two phases: a NaCl-type solid solution phase with a cored structure surrounded by a solid solution consisting of one or more of Ta, Nb, and Zr carbides, tungsten carbide, titanium carbide, and titanium nitride, and a titanium nitride phase. It has a structural structure, and the binder phase is Co in which W and Ti are dissolved in solid solution, or Co.
characterized by having a structure consisting of and Ni,
Cermet for cutting tools.