JPS634896B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention has high hardness and high toughness, and exhibits excellent wear resistance and chipping resistance especially when used as a cutting tool, and provides excellent cutting performance over a long period of time. It is related to the performance of cermets. [Conventional technology and its problems] Conventionally, in cermets for cutting tools, the main part of the hard dispersed phase is composed of titanium carbide (hereinafter referred to as TiC), while the main part of the binder phase is composed of either Ni or Co. TiC-based cermets are known that are composed of two or both of these materials, but although these TiC-based cermets have high hardness, they have poor toughness, so they are prone to cracking when used under cutting conditions that require toughness. This makes it impractical for practical use. In addition, in recent years, cermets for cutting tools with high hardness and high toughness have been developed in which the main part of the hard dispersed phase is composed of titanium carbonitride (hereinafter referred to as TiCN).
On the other hand, a TiCN-based cermet in which the main part of the binder phase is similarly composed of either Ni and/or Co has been proposed, but this TiCN-based cermet has poor sinterability and therefore has poor properties. It has large variations and is unreliable. [Means for Solving the Problems] Therefore, from the above-mentioned viewpoints, the present inventors have developed a material that has high hardness and high toughness, has consistent properties, and is excellent when used as a cutting tool. As a result of our research to develop a cermet that exhibits excellent cutting performance, we found TiC powder, tantalum carbide (hereinafter referred to as TaC) powder, niobium carbide (hereinafter referred to as NbC) powder, and two types of these as raw material powders. In addition to the above solid solution powder, titanium nitride (hereinafter referred to as TiN) powder,
Tantalum nitride (hereinafter referred to as TaN) powder, niobium nitride (hereinafter referred to as NbN) powder, Ni powder, and
Co powder is prepared, these raw material powders are blended into a predetermined composition, mixed under normal conditions, and a green compact is press-molded, and then the green compact is placed in a vacuum atmosphere until a liquid phase appears. 0.1~10torr after liquid phase appearance
When sintered in a nitrogen atmosphere with a pressure within the range of , the hard dispersed phase has a cored structure of 70 to 90% by weight. (a) Ti and Ta composite carbonitride; (b) It consists of a composite carbonitride of Ti, Ta and Nb (however, Nb is 50 atomic% or less of Ta), and one of the above (a) and (b), while the remaining 10 to 30% by weight of the binder phase is ,weight%
Contains Ti: 0.5 to 5%, Ta or Ta and Nb (however, Nb is 50% or less of Ta): 0.1 to 3% as a solid solution, and the remainder is Ni and/or Co. When the hard dispersed phase is expressed by the composition formula: {Ti〓(Ta, Nb)〓}(C _x N _y ) _z , the atomic ratio is: , α+β=1, x+y=1, 0.6≦α≦0.9, 0.50≦x≦0.90, 0.1≦β≦0.4, 0.10≦y≦0.50, 0.85≦z≦1.00, and the presence of the above-mentioned hard dispersed phase. The core part that makes up the core structure is
Composition consisting of Ti: 45-49.5%, Ta or Ta and Nb (however, Nb is 50% or less of Ta): 0.5-5%, C: 25-45%, N: 5-25% in atomic percent. On the other hand, the same periphery has the same atomic % Ti: 25-45%, Ta or Ta and Nb (however, Nb is 50% or less of Ta): 5-25%, C: 35-47.5% , N: 2.5-15%, furthermore, the C content is higher in the peripheral area than in the core area, and the N content is higher in the peripheral area than in the core area.
A cermet with a higher concentration distribution in the core than in the periphery can be obtained, and the resulting cermet has high hardness and toughness, as well as good sinterability, so it has good properties. There is no variation in , so when this is used as a cutting tool,
They found that it stably exhibits excellent wear resistance and chipping resistance. This invention has been made based on the above knowledge, and the reasons for the limitations on cermets will be explained below. (a) Content of hard dispersed phase and binder phase The hard dispersed phase has the effect of increasing the hardness of cermet and significantly improving its wear resistance, but its proportion in the cermet is 70% by weight. If the proportion of the binder phase is relatively too large, exceeding 30% by weight, the wear resistance of the cermet will decrease significantly, while if the proportion of the binder phase exceeds 90% by weight, If the proportion of the binder phase is relatively less than 10% by weight, the chipping resistance of the cermet will be significantly reduced, so the proportion thereof was set at 70 to 90% by weight relative to the entire cermet. (b) Value of α in the composition formula of the hard dispersed phase Ti is the main component of the hard dispersed phase, and
It mainly forms the core of the cermet and has the effect of improving the hardness and wear resistance of the cermet, but its proportion (atomic ratio) to the metal components of the hard dispersed phase is less than 0.6. However, if the ratio exceeds 0.9, the toughness of the cermet will decrease and the fracture resistance will deteriorate. Metal component (α+β=1)
In other words, the value of α is expressed as an atomic ratio.
It was set at 0.6 to 0.9. (c) Value of β in the composition formula of the hard dispersed phase Ta is also a component that forms the hard dispersed phase, and the oxidation resistance of cermets is improved by the inclusion of Ta, but the proportion is the same as that of the hard dispersed phase. If the ratio (atomic ratio) to the metal component is less than 0.1, the desired effect of improving oxidation resistance cannot be obtained, while if the ratio exceeds 0.4, the hard dispersed phase will soften and the wear resistance of the cermet will decrease. Therefore, the proportion of Ta in the metal component of the hard dispersed phase, that is, the value of β, can be determined in terms of atomic ratio.
It was set as 0.1 to 0.4. Note that a portion of Ta is replaced with Nb within a range of 50 atomic % or less.
Since the characteristics of the cermet are not impaired even when substituted with Nb, the inclusion of Nb is allowed in coexistence with Ta. (d) Values of x and y in the composition formula of the hard dispersed phase Both the C component and the N component constitute the hard dispersed phase, and the C component improves the hardness of the hard dispersed phase, thereby improving the hardness of the cermet. However, if the ratio (atomic ratio) to the total of C and N (x + y = 1) is less than 0.50, the desired excellent wear resistance cannot be achieved. , while the ratio is 0.90
If it exceeds 100%, the hard dispersed phase becomes too hard and the fracture resistance of the cermet decreases, and the N component suppresses the grain growth of the hard dispersed phase and improves the toughness (fracture resistance) of the cermet. ), but if the ratio is less than 0.10, the desired excellent fracture resistance cannot be secured, while if the ratio exceeds 0.50, the wear resistance of the cermet will decrease. Therefore, the proportions of C and N components, that is, the values of x and y, are x: 0.50 to 0.90, y: 0.10, respectively.
~0.50. (e) Value of z in the compositional formula of the hard dispersed phase The value of z is the C that constitutes the hard dispersed phase.
and the ratio (atomic ratio) of the total of the same metal components to the total of the N components. If the value is less than 0.85, the fracture resistance of the cermet is significantly reduced, so the lower limit of z was set at 0.85. Note that even if the upper limit of z is 1.0, which is the stoichiometric composition, the properties of the cermet will not be impaired.
It was set as 1.0. The value of z is mainly determined by the amount of N in the cermet and the partial pressure of nitrogen in the sintering atmosphere; the larger the amount of N in the cermet and the lower the partial pressure of nitrogen in the sintering atmosphere, the smaller the value of z. As a result, the wear resistance of the cermet is improved, but the chipping resistance is reduced. (f) Composition of the core and periphery of the hard dispersed phase When α and β and the values of x, y, and z in the compositional formula of the hard dispersed phase satisfy the above conditions, the composition of the core and the periphery will inevitably change. The composition is Ti: 45-49.5%, Ta or Ta+Nb: 0.5-5%, C: 25-45%, N: 5-25% in atomic %, and the composition of the peripheral part is Ti: 25-49.5%. 45%, Ta or Ta + Nb: 5 to 25%, C: 25 to 47.5%, N: 2.5 to 15%, and therefore α, β, x,
If any of the values of y and z deviate from the above range, the composition of the core and peripheral parts will deviate from the above range, and at least one of the wear resistance and chipping resistance of the cermet will decrease. They will come to do so. (g) Composition of the binder phase (1) Ti The Ti component is dissolved in the matrix of the binder phase and has the effect of improving the wear resistance (hardness) of cermets, but its content is If the proportion is less than 0.5%, the desired wear resistance cannot be achieved, while if the content exceeds 5%, the binder phase becomes brittle and the fracture resistance of the cermet deteriorates. Therefore, its content was determined to be 0.5 to 5% in proportion to the binder phase (the same applies hereinafter). (2) Ta The Ta component also dissolves in the binder phase and has the effect of improving the oxidation resistance of cermets, but if its content is less than 0.1%, the desired oxidation resistance cannot be obtained; exceeds 3%,
Similar to Ti, the binder phase becomes brittle and the fracture resistance of the cermet decreases, so its content was set at 0.1 to 3%. Note that even if a portion of Ta is replaced by Nb within a range of 50% or less, no change appears in the cermet properties, so the coexistence of Nb and Ta is allowed. [Example] Next, the cermet of the present invention will be specifically explained with reference to Examples. As raw material powders, various titanium carbonitride powders having the compositions shown in Table 1 and having an average particle size within the range of 1 to 1.5 μm, TaC powder with a diameter of 1.1 μm, and NbC powder with a diameter of 1.0 μm are used as raw material powders. , 2.2 μm Ni powder, and 1.2 μm Co powder were prepared, and these raw material powders were blended into the composition shown in Table 1, wet mixed in a ball mill for 72 hours, dried, and then weighed 15 kg. /mm ² pressure into a green compact, and then this green compact is heated to 1330 mm in a vacuum of 10 ^-2 torr.
After heating to a predetermined liquid phase appearance temperature in the range of ~1430°C, the atmosphere is replaced with nitrogen having a predetermined nitrogen partial pressure in the range of 3 to 10 torr.

【table】

[Table] 1450 to 1500 in this nitrogen atmosphere instead of the atmosphere
Cermets 1 to 16 of the present invention and Comparative cermets 1 to 7 were produced by heating to a predetermined maximum temperature within the range of 0.degree. C. and sintering under conditions of holding at this maximum temperature for 1 hour. Next, the resulting cermet 1 of the present invention
~16 and comparative cermets 1 to 7 were analyzed for their component compositions using conventional analysis methods and EPMA (electronic probe microanalyzer), and the results are shown in Tables 2 and 3, respectively. The hard dispersed phase of each cermet had a cored structure. In addition, the composition of the core part and the peripheral part of a hard dispersed phase was shown by the average value of the result of measuring five hard dispersed phases. Furthermore, the compositions of Comparative Cermets 1 to 7 are outside the scope of the present invention. Next, for the present invention cermets 1 to 16 and comparative cermets 1 to 7, Rockwell hardness (A scale) was measured for the purpose of evaluating wear resistance, and transverse rupture strength was measured for the purpose of evaluating fracture resistance (toughness). that

[Table] (*mark: outside the scope of the present invention)

[Table] Each was measured and then used as a cutting tool. Work material: SNCM439 (Hardness: H _B 260) round bar, Cutting speed: 160m/min, Feed: 0.3mm/rev., Depth of cut. : 1.5mm, Cutting time: 15mm, Continuous cutting test of steel under the conditions, Work material: SNCM439 (hardness: H _B 280) square material, Cutting speed: 140m/min, Feed: 0.26mm/rev An interrupted cutting test was conducted on steel under the conditions of ., depth of cut: 2 mm, cutting time: 3 min, and in the continuous cutting test on steel, the flank wear width and rake face wear depth of the cutting edge were measured. In the cutting test, the number of broken cutting edges out of 10 tested cutting edges was measured. The results of these measurements are shown in Table 4. Also,
Table 4 shows commercially available TiC for comparison purposes.
based cermet (hereinafter referred to as conventional cermet 1) and TiCN-based cermet (hereinafter referred to as conventional cermet 2).

〔Effect of the invention〕

As is clear from the results shown in Tables 1 to 4, the cermets 1 to 16 of the present invention all have high hardness and high toughness, and in the cutting test, they showed much better wear resistance than conventional cermets. On the other hand, comparative cermets 1 to 7 having compositions outside the scope of the present invention had low hardness and/or toughness, and were accordingly inferior in cutting tests. It only shows the cutting results. As mentioned above, the cermet of the present invention has high hardness and high toughness, so it exhibits excellent cutting performance over a long period of time, especially when used as a cutting tool that requires these characteristics. .

Claims (1)

[Claims] 1. A composite carbonitride of Ti and Ta, in which the hard dispersed phase has a cored structure of 70 to 90% by weight, or Ti and
Ta and Nb (however, Nb is less than 50 atomic% of Ta)
of composite carbonitride, while the remaining 10-30% by weight of the binder phase is
Contains Ti: 0.5 to 5%, Ta or Ta and Nb (however, Nb is 50% or less of Ta): 0.1 to 3% as a solid solution, and the remainder is one or two of Ni and Co. When the hard dispersed phase is expressed by the composition formula: {Ti〓(Ta, Nb)〓}(C _x N _y ) _z , atoms In terms of ratio, α+β=1, x+y=1, 0.6≦α≦0.9, 0.50≦x≦0.90, 0.1≦β≦0.4, 0.10≦y≦0.50, 0.85≦z≦1.00, and the above hard dispersed phase The core part that makes up the cored structure of
Composition consisting of Ti: 45-49.5%, Ta or Ta and Nb (however, Nb is 50% or less of Ta): 0.5-5%, C: 25-45%, N: 5-25% in atomic percent. On the other hand, the same periphery has the same atomic % Ti: 25-45%, Ta or Ta and Nb (however, Nb is 50% or less of Ta): 5-25%, C: 35-47.5% , N: 2.5-15%, A cermet for cutting tools having high hardness and high toughness.