JPH024932A - Manufacture of cutting tool made of diamond-coated tungsten carbide base sintered hard alloy - Google Patents

Abstract

PURPOSE:To manufacture the title cutting tool made of a sintered hard alloy in a short time by subjecting a green compact to which prescribed ratios of WC powder and Co powder are blended to primary sintering, HIP and secondary sintering and thereafter forming an artificial diamond-coated layer thereon. CONSTITUTION:WC powder and Co powder are blended in the prescribed blending compsn. and are mixed under ordinary conditions to compact into a green compact, which is thereafter subjected to primary sintering at 1400 to 1500 deg.C in vacuum. The primary sintered body is then subjected to hot isostatic pressing under the conditions of 1300 to 1500 deg.C temp. and 100 to 1000 atmospheric pressure to extinguish pores and is thereafter subjected to secondary sintering at 1400 to 1500 deg.C in vacuum to uniformly distribute a Co phase. In such a manner, the matrix of a WC-based sintered hard alloy constituted of, by weight, 0.1 to <1% Co and the balance WC with inevitable impurities and having >=99% theoretical density ratio is formed, and, after that, an artificial diamond-coated layer is formed on the surface of the matrix by a low pressure-vapor phase synthesizing method. By this method, the deposition compacting speed of the artificial diamond-coated layer can be increased to manufacture a cutting tool in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to diamond-coated tungsten carbide (hereinafter referred to as W
The present invention relates to a method for manufacturing a cutting tool made of a hard metal base material (denoted by C).

[Conventional technology]

In recent years, diamond-coated WC-based cemented carbide cutting tools have been proposed as cutting tools that exhibit excellent cutting performance for cutting Hep alloys, Cu alloys, and non-metals.

This diamond-coated WC-based cemented carbide cutting tool uses WC powder, Co powder, and carbon powder as raw material powders, and these raw material powders are mixed in a predetermined manner, as described in, for example, Japanese Patent Application Laid-Open No. 63-45372. Co
a1~4%, finely and uniformly dispersed free carbon/l5O (International 5 standard
zation Organization) standard.
01 to CO8, and the remainder is WC and unavoidable impurities. Forming an artificial diamond coating layer on the surface using a low-pressure vapor phase synthesis method such as a chemical vapor deposition method (CVD method) using thermal decomposition of a gas such as CH4 or a physical vapor deposition method (PVD method) that bombards a substrate with carbon ions. Manufactured by.

[Problem to be solved by the invention]

However, in the conventional method for manufacturing diamond-coated WC-based cemented carbide cutting tools described above, it takes a relatively long time to form the artificial diamond coating layer, and the artificial diamond coating layer can be formed at a faster precipitation rate. Formation of layers is desired.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to enable the formation of an artificial diamond coating layer at a faster precipitation formation rate. A low CO content of less than 1% and a uniform distribution of it will further increase the rate of diamond precipitate formation, while a reduction in Co content will significantly reduce the strength of the substrate. W.C.C.
When producing a cemented carbide substrate, sintering is performed without adding carbon powder as a raw material powder. (a) First, a green compact is heated to
``Primary sintering is performed at a temperature of 0°C, (b) Then, this primary sintered material is heated at a temperature of 130°C.
Hot isostatic pressing (HIP) was performed under the conditions of 0 to 1500°C and pressure: 100 to 1000 atm.
If secondary sintering is performed at a temperature of ~1500°C, through the three steps (a) to (C) above, 95~
The primary sintered grain, which had a theoretical density ratio of 98%, disappeared in the HIP treatment in step (b), and now has a theoretical density ratio of 99% or more, and is further sintered. Even after the HIP treatment, Co is aggregated, that is, many Co pools are seen, or Co is uniformly distributed by the above step (c), and the WCC cemented carbide substrate in such a state, 1 to 4, including no free carbon formation.
In addition to having a strength equal to or higher than that with a high Co content of %, we also found that the formation of diamond precipitates was significantly promoted by a structure in which relatively low CO content was uniformly distributed. I got it.

Therefore, this invention has been made based on the above knowledge, and uses WC powder and Co powder as raw material powders, blends these raw material powders into a predetermined composition, and under normal conditions,
After mixing and forming into a green compact, (a) this green compact is subjected to primary sintering in a vacuum at a temperature of 1400 to 1500°C, (b) then, this primary sintered material is Temperature: 130
Hot isostatic pressing was performed under the conditions of 0 to 1500°C and pressure = 100 to 100 atmospheric pressure to eliminate the pores, (c)
Furthermore, this hot isostatic press mill was subjected to secondary sintering in a vacuum at a temperature of 71,400 to 1,500°C to produce Co.
The three-step sintering steps (a) to (c) were performed to ensure uniform phase distribution, and Co:0.
1 to less than 1% by weight, with the remainder consisting of WC and unavoidable impurities, and having a theoretical density ratio of 99% or more, the WCC cemented carbide The present invention is characterized by a method for manufacturing a diamond-coated WC-based cemented carbide cutting tool, which comprises forming an artificial diamond coating layer on the surface of a substrate by a low-pressure vapor phase synthesis method.

Next, the reason why the manufacturing conditions are limited as described above in the method of this invention will be explained.

(a) Primary sintering temperature If the temperature is lower than 1400°C, sintering will be insufficient and a large number of pores and Co pores will be present, and as a result, the HIP treatment in the post-process will have a sufficient effect of eliminating pores. On the other hand, if the temperature exceeds 1500°C, the WC grains become coarser and the Co evaporates and scatters, making it impossible to secure the desired strength.
The temperature was set at 400-1500°C.

(b) HIP conditions Even if the temperature is less than 1300°C or the pressure is less than 100 atm, pores cannot be sufficiently eliminated, and therefore a substrate with a theoretical density ratio of 99% or more cannot be manufactured. On the other hand, if the temperature exceeds 1500℃,
The WC grains become coarser and the strength decreases, and if the pressure exceeds 1000 atm, gas will be drawn in and cause pores. Pressure = 100-100
The pressure was set at 0 atmospheric pressure.

(c) Secondary sintering temperature If the temperature is less than 1400°C, it is difficult to uniformly distribute the Co phase pool, while if the temperature exceeds 1500°C, the WC grains will become coarser and Co will evaporate and scatter. The temperature was set at 1,400 to 1,500°C because this caused a decrease in strength.

(d) Co content If the Co content is less than 0.1%, it is not only impossible to secure the desired strength, but also the toughness is low, and the cutting edge is likely to be damaged during cutting. If the content exceeds 1%, the rate of diamond precipitate formation rapidly decreases, so the content was set at 0.1 to less than 1%.

(c) Theoretical density ratio Since the Co content of the WCC cemented carbide substrate of this invention is low at less than 1%, the HIP treatment is performed so that the substrate has a theoretical density ratio of 99% or more, CO: 1 to 4. % and has a theoretical density ratio of about 95 to 98%.
Therefore, with a theoretical density ratio of less than 99%, it is not possible to secure a predetermined strength.

〔Example〕

Next, the method of the present invention will be specifically explained using examples.

As raw material powders, WC powder and CO powder, both of which have a predetermined average particle size within the range of 1 to 3.2 txn, are prepared, these raw material powders are blended into a predetermined composition, and the mixture is heated in a ball mill for 72 hours. After time mixing and drying, 1.5
Press molded into a green compact at a pressure of Lon/c-, then,
This green compact was sintered under the conditions shown in Table 1, and the composition, transverse rupture strength (strength evaluation),
A WCC cemented carbide substrate having a theoretical density ratio of Using one type of thermionic emission method, reaction vessel: 120 mm diameter quartz tube, filament used: metallic tungsten, filament temperature: 2000°C, substrate temperature near 50°C, atmosphere: 10 torr CH4+H2, reaction gas ratio: CH4+H2= Methods 1 to 9 of the present invention and conventional methods 1 to 4 were performed by performing diamond coating under the following conditions: 0.005, reaction time: 12 hours, and forming a diamond coating layer with the average layer thickness shown in Table 1. Each test was carried out to produce a diamond-coated WC-based cemented carbide cutting tool (hereinafter referred to as a coated cutting tool).

Next, regarding the various coated cutting tools obtained as a result, the following information was given: Work material, round bar of Aρ-18% St alloy, cutting speed: 1
50rn/mj opening, feed rate: 0.1mm/blade, depth of cut: 1mm.

A lathe cutting test was conducted under the following conditions, and the cutting time until the flank wear width of the cutting edge reached 0.3+on+ was determined.

The results are shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, it can be seen that the coated cutting tools manufactured by the methods 1 to 9 of the present invention have a higher Co content than the coated cutting tools manufactured by the conventional methods 1 to 4, although the Co content in the substrate is low. It has higher strength and density than a Co-containing substrate, and in Methods 1 to 9 of the present invention, it has a higher strength and density than in conventional methods 1 to 4, despite the same artificial diamond coating layer formation conditions. It is clear that the formation of artificial diamond coatings with high precipitate formation rates is possible and that a corollary of this is that cutting tests show relatively long cutting times.

As described above, according to the method of the present invention, the rate of precipitation of the artificial diamond coating layer is fast, and a diamond-coated WC-based cemented carbide cutting tool can be manufactured in a correspondingly short time.

Claims (1)

[Claims] (1) Tungsten carbide powder and C as raw material powder
After blending these raw material powders into a predetermined composition using O powder, mixing them under normal conditions, and forming them into a compact, (b) Then, this primary sintered material is subjected to primary sintering at a temperature of 1300 to 1
Hot isostatic pressing was performed at 500°C and a pressure of 100 to 1000 atm to eliminate pores. Perform secondary sintering at temperature C
Co:0.
1 to less than 1% by weight, with the remainder consisting of tungsten carbide and unavoidable impurities, and having a theoretical density ratio of 99% or more, the tungsten carbide A method for manufacturing a diamond-coated tungsten carbide-based cemented carbide cutting tool, which comprises forming an artificial diamond coating layer on the surface of a cemented carbide-based substrate by low-pressure vapor phase synthesis.