JPS592731B2 - Super hard alloy parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cemented carbide member having extremely high toughness.

Conventionally, it contains tungsten carbide (hereinafter referred to as WC) as a main component, and contains COI, Fe, Ni, and Cr.

A superhard alloy member is known which has a composition containing 2 to 20% by weight of a Co-based alloy containing one or more of Mo and Mo in a range of 50% by weight or less as a binder phase forming component. Although this conventional cemented carbide material has excellent wear resistance, it has low toughness, so it cannot be used in fields that require high toughness such as heavy cutting, hole drilling, and gear cutting. It was limited.

The present inventors conducted research to impart toughness to the conventionally known WC-Co based cemented carbide member (hereinafter simply referred to as "conventional cemented carbide member") from the above-mentioned viewpoints, and the results were as follows: (a) After examining the defects and fractures of the conventional cemented carbide members mentioned above, it was found that most of the defects and fractures in these members are caused by cracks from the surface thereof.

(b) When producing the conventional cemented carbide member, one or both of nitride and carbonitride solid solutions of one or more metals from groups 4a, 5a and 6a of the periodic table ( (hereinafter collectively referred to as metal carbon/nitrides) are mixed as a raw material powder, and when a green compact formed from this mixed powder is sintered in a decarbonized atmosphere under reduced pressure, the surface of the sintered member In addition, a surface softening layer is formed which has lower hardness than the inside and is composed of a W C-Co alloy phase (a small amount of metal carbon/nitride may be present).

(C) The thickness and hardness of the surface softening layer can be adjusted by adjusting the carbon/nitride content of the metal and the carburizing atmosphere conditions.

(d) The sintered member having the surface softening layer includes:
No defects or destruction shall occur.

The findings shown in (a) to (d) above were obtained.

This invention was made based on the above knowledge, and contains 20.5 to 50% by weight of metal carbon/nitride, Co or C.
O-based alloy: 2-20% by weight, WC and inevitable impurities:
The remainder has a composition consisting of the following, and is characterized by a surface softening layer having a hardness 5 to 50% lower in Vickers hardness than the internal hardness over a thickness of 5 to 100 μm from the surface. It is.

Next, the reason why the composition range and the thickness and hardness of the surface softening layer are limited as described above in the superhard alloy member of the present invention will be explained.

(a) Carbon and nitrides in metals Carbon and nitride components in metals have the effect of increasing the strength of parts and improving crater resistance when used as cutting tools. During sintering, W C-C is mainly formed on the surface in relation to the sintering atmosphere.
o It has the effect of forming a tough surface softening layer consisting of an alloy phase, but if its content is less than 0.5% by weight, the desired effect cannot be obtained, whereas if it is contained in an amount exceeding 50% by weight. Since the WC content becomes too low relative to the
It was set at 50% by weight.

(b) Co or Co-based alloy Co or Co-based alloy is a component forming a binder phase,
If the content is less than 2% by weight, the toughness will decrease, while if the content exceeds 20% by weight, the W
If the content of C becomes too low, the wear resistance deteriorates, making it impossible to use it as a cutting tool, so the content was set at 2 to 20% by weight.

(C) Thickness of the surface softening layer If the thickness is less than 5 μm, the effect of suppressing the occurrence of cracks on the surface of the member will not be sufficient, while if the thickness exceeds 100 μm, initial wear will increase. Sao 5-1
00 μm.

(d) Hardness of the surface softening layer: If the degree of softening of the surface softening layer relative to the inside of the member is less than 5% in terms of Vickers hardness, the desired cracking suppression effect cannot be secured because the hardness difference is insufficient. If the hardness exceeds 50% in one direction, the surface softening layer will become too soft compared to the inside of the component, and significant initial wear will occur. In comparison, the Vickers hardness was set to be 5 to 50% lower.

Although there is no problem even if there is a hardness gradient in the surface softening layer, the condition that the degree of softening relative to the internal hardness of the member is 5 to 50% lower in terms of Vickers hardness defined above must be satisfied.

Next, the cemented carbide member of the present invention will be explained using Examples while comparing with Comparative Examples.

Example 1 Final component composition is WC-10% by weight TiN-10% by weight T
aC-10% by weight of Co, commercially available W
Blend C powder, TiN powder, TaC powder, and Co powder, mix this blended powder, mold a green compact from this mixed powder, and sinter the green compact under the sintering conditions shown in Table 1. sintering temperature, sintering holding time, and sintering atmosphere) to produce the superhard alloy member of the present invention (hereinafter referred to as the member of the present invention).
1.2, and comparative cemented carbide members (hereinafter referred to as comparative members) 1 and 2 were manufactured, respectively.

Note that Comparative Member 1 has a softened surface layer with a thickness lower than the range of the present invention, and Comparative Member 2 does not have a softened surface layer.

Table 1 also shows the internal hardness of the members, the thickness and hardness of the softened surface layer of the members 1 and 2 of the present invention and comparative members 1 and 2.

Next, the above-mentioned members 1 and 2 of the present invention and comparative members 1 and 2
Regarding, work material knee 545C (hardness Hv: 200), tool shape:
Holder: N11R-44, Tip: 5NP432 (no honing), Cutting speed:
60m/min.

Feed: 0.45m71t/m1n1 Depth of cut: 2mm1 Cutting time: 5.10, and 15 m1n.

A continuous cutting test was conducted under the following conditions, and the amount of flank wear was measured.

The results are shown in Table 2. Further, the above-mentioned member 1 of the present invention,
2, and comparison member 121 - [Work material: SNCM-8 (hardness Hv: 300), tool shape: holder: N11R-44, tip: 5NP432 (no honing), cutting speed:
60m/min.

Feed: 0.5, 0.6, 0.7, and 0.8W/r
ev,, cut depth: 2 myn.

Cutting time: 2m1n.

An interrupted cutting test was conducted under the following conditions, and it was determined how many of the three pieces were broken.

The results are also shown in Table 2.

As is clear from the results shown in Table 2, although the members of the present invention and the comparative members show almost the same performance in terms of wear resistance as seen in the continuous cutting test, they do not show the same performance in the interrupted cutting test. It can be seen that the inventive member exhibits cutting performance that is one level better than the comparative member, and has excellent toughness.

Example 2 Commercially available raw material powders were blended so as to have the final component compositions shown in Table 3, and after mixing under normal conditions, a green compact was formed from this, and then the green compact was Sintering was carried out under the conditions of sintering temperature: 1400°C, sintering time: 1 hour, sintering atmosphere: pressure 1 x 10-'' Co-containing carburizing gas with condensed Hg, and inventive members 3 to 10 and comparative members were obtained. 3~
5 were produced respectively.

Comparative member 3 has a surface softening layer with a thickness lower than the range of the present invention, and comparative member 4 has a metal carbon/nitride content higher than the range of the present invention, and the surface softening layer is lower than the range of the present invention. The layer thickness is also on the lower side, and comparative member 5 has no surface softening layer formed.

Further, Table 3 shows the internal hardness of the members, the thickness and hardness of the softened surface layer, and the transverse rupture strength of the members 3 to 10 of the present invention and the comparative members 3 to 5.

Next, regarding the present invention members 3 to 10 and comparative members 3 to 5, work material: SNCM-8 (hardness Hv: 300), tool shape: holder: N11R-44, tip: 5NP432 (no honing), cutting speed:
60m/min.

Sending: 0.6 dragon, Cutting time: 2m1n.

An interrupted cutting test was conducted under the following conditions, and the defect situation was observed in the same manner as in Example 1.

The observation results are also shown in Table 3.

From the results shown in Table 3, it is clear that the members of the present invention all have higher strength and extremely superior toughness than the comparative members.

As mentioned above, the cemented carbide member of the present invention has extremely excellent toughness, so it can be used particularly in heavy cutting, hole machining, and gear cutting, which conventional cemented carbide members are not good at. It exhibits excellent cutting performance when used for cutting.

Claims (1)

[Scope of Claims] 1. Nitride and/or carbonitride solid solution of one or more metals of Groups 4a, 5a, and 6a of the Periodic Table, 20.5~ 50% by weight, Co or Co-based alloy: 2-20% by weight, tungsten carbide and unavoidable impurities: the remainder.
A superhard alloy member having a surface softening layer having a Vickers hardness 5 to 50% lower than the internal hardness over a thickness of 0 μm.