JPS61297003A - Cutting tool made of surface-coated tungsten carbide base sintered hard alloy for high-speed cutting - Google Patents

Abstract

PURPOSE:To increase resistance of the cutting tool in the head line against plastic deformation so as to make it possible to use it for a long duration by specifying content of bonding-phase forming constituent in the internal of base body of a cutting tool made of surface-coated tungsten carbide base sintered hard alloy for high-speed cutting. CONSTITUTION:The internal of the base body is constituted from WC base sintered hard alloy which is constituted from dispersion-phase forming constitutent of NaCl-type crystal-structured compound : 2-20%, bonding-phase forming constituent of Co, or Co and Ni of 1.5-2.0% and the like, and the residuals of WC and inevitable impurities. And the surface portion across the thickness range from 2 to 100mum is constituted form a surface softening layer, which is constituted from Co, or Co and Ni 4-20%, and the residual of WC and inevitable impurities, and moreover the content of Co, or sum of Co and Ni is 210-500% higher than the same content of the internal of the base body. This surface softening layer is formed under the specific conditions of pressure, temperature and time under nitrogen atmosphere at a part of the sintering process. The cutting tool made of surface-coated WC base sintered hard alloy thus manufactured has excellent characteristics of abrasion-resistance, therefore, the tool is suited to high-speed cutting.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a surface that exhibits excellent plastic deformation resistance, particularly when used in high-speed cutting where this property is required. This invention relates to a cutting tool made of coated tungsten carbide (hereinafter referred to as WC) cemented carbide.

[Conventional technology]

Conventionally, generally, as a cutting tool, 4a and 5a of the periodic table as dispersed phase forming components.

and carbides, nitrides, and carbonitrides of group 6a metals,
and a Na CQ type crystal structure compound consisting of a solid solution of two or more of these: 2 to 20%.

Co or Co and Ni as bonded phase forming components: 5~
10%.

and, if necessary, as a dispersed phase forming component i. carbon: 0.02 to 0.4
%.

, and the remainder essentially consists of WC and unavoidable impurities (the above weight %, below % shows weight %)
On the surface of the CC cemented carbide substrate, Ti carbides, nitrides, and oxides (hereinafter referred to as TtC, TiN, and TiO, respectively), and solid solutions of two or more of these,
Furthermore, a surface formed by forming a coating layer consisting of a single layer or a multilayer of two or more types of aluminum oxide (hereinafter referred to as Affi 203) with a predetermined average thickness within the range of 1 to 20 μm. Coated WCC cemented carbide is used.

[Problem that the invention seeks to solve]

However, when using the above-mentioned conventional surface-coated WCC cemented carbide cutting tools for high-speed cutting at a cutting speed of 350 m/1n or higher, where the heat generation is large and the cutting edge becomes extremely hot, plasticity It is easy to deform, and as a result, the dimensional accuracy of the workpiece decreases (= 5 -), and the cutting edge itself begins to wear abnormally, leading to the end of its service life in a relatively short period of time. Ta.

[Means for solving problems]

Therefore, from the above-mentioned viewpoint, the present inventors focused on a cutting tool made of conventional surface-coated WCC cemented carbide, and created a cutting tool that imparts excellent plastic deformation resistance to the cutting tool and has a cutting speed of 350 mm.
As a result of conducting research to develop a surface-coated WCC cemented carbide cutting tool that can be used for high-speed cutting of m/min or higher, we found that the binder phase forming component inside the base of the surface-coated WCC cemented carbide cutting tool The content of 1.5 to 2.
If the plastic deformation resistance is significantly lowered to 9%, the plastic deformation resistance will be significantly improved, while the accompanying decrease in toughness can be compensated for by the surface softening layer formed on a part or all of the base surface. Even if a crack occurs inside the base, its progression will be completely suppressed by the surface softening layer, making it possible to use it as a cutting tool for high-speed cutting over a long period of time. There are 19 findings.

This invention was made based on the above findings, and includes TiC, TiN on the surface of a WCC cemented carbide base.

A surface-coated WC formed by forming a coating layer consisting of Ti O, a solid solution of two or more thereof, and a single layer of one type of Affi203 or a 'Ki layer of two or more types of Affi203.
In the C cemented carbide cutting tool, the inside of the base is dispersed phase forming components 4a and 5a of the periodic table.

and carbides, nitrides, and carbonitrides of group 6a metals,
and a NaCl type crystal structure compound consisting of a solid solution of two or more of these: 2 to 20%.

Co or co and Ni as bonded phase forming components:
1.5-2.9%.

and, if necessary, free carbon as a dispersed phase forming component: 0.02 to 0.4
%.

, and the remainder is substantially WC as a dispersed phase forming component.
A WCC cemented carbide having a composition consisting of unavoidable impurities is formed, and a part or the entire surface of the base is covered with Co, or Co and N1, over a depth of 2 to 100 μm from the surface of the base. 4-20%.

, with the remainder essentially consisting of WC and unavoidable impurities, and the content of Co or Co and Ni is 210% compared to the content of Co or Ni such as Co inside the substrate. It is characterized by being composed of ~500% more surface softening layers.

It should be noted that the surface softening layer on the surface of the substrate in the surface-coated WCC cemented carbide cutting tool of the present invention is produced by a normal powder metallurgy method in which the atmosphere of the sintering process including the temperature raising process is evacuated, for example. It can be formed by setting a part of the atmosphere in the sintering process including the temperature raising process to a nitrogen atmosphere.

Next, in the surface-coated WCC cemented carbide cutting tool of the present invention, the reason why the component composition and the depth and thickness of the surface softening layer are limited as described above will be explained.

Δ, component composition inside the substrate (a) Na C1 type crystal structure These components have wear resistance and plasticity resistance as well as WC, which is a dispersed phase forming component, in relation to the content of binder phase forming components. It has the effect of increasing or decreasing deformability, but
If the content is less than 2%, the desired effect cannot be obtained, while if the content exceeds 20%, the toughness will be significantly reduced and cracks will easily occur during practical use. Therefore, its content was determined to be 2 to 20%.

(b) Go, Co and Ni These components act as bonded phase forming components,
If the content is less than 1.5%, cracks will easily occur during practical use, and the surface softening layer will not be able to suppress the cracks. On the other hand, if the content exceeds 2.9%, the desired excellent durability will not be achieved. Since plastic deformability cannot be ensured, its content is set at 1.5 to 2.9%.

(C) Free carbon This component forms a dispersed phase and has the effect of stopping the progression of cracks generated inside the substrate at their existing positions (the reason for this is that when the tip of a crack collides with free graphite, the radius of curvature (It is understood that the growth of cracks is suppressed by increasing the I! However, if the content is less than 0.02%, the desired effect cannot be obtained, while if the content exceeds 0.4%, the toughness will be significantly lowered.
．． It was set at 02-0.4%.

B0 surface softening layer (a) Content of Co or Co and Ni These components exist in large amounts compared to the content inside the base, and have the effect of improving the toughness of the entire tool. The surface softening layer is made softer than the inside of the base, thereby eliminating cracks! 1'1 It has the effect of increasing the temperature, but its content is 4%.
If the content is less than 20%, the desired effect cannot be obtained; on the other hand, if the content exceeds 20%, it becomes too soft and the coating layer is likely to peel off during practical use. It was set as 0%.

(b) If Go, or the ratio of Co and Ni to that inside the base body, or the ratio of Co and N1 to the content of Co or Co and Ni inside the base body, is less than 210%, the desired toughness improvement is not achieved. On the other hand, even if the ratio exceeds 500%, no further improvement effect can be obtained due to the above action, and the plastic deformation resistance decreases in relation to the thickness of the surface softening layer. Therefore, the ratio was set at 210% to 500%.

(C) Thickness and Depth) If the thickness is less than 2 μm, the desired toughness improvement effect and crack propagation suppressing effect cannot be obtained;
If the thickness exceeds 00 μm, the plastic deformation resistance decreases, so the thickness was determined to be 2 to 100 μm.

〔Example〕

Next, the surface-coated WCC cemented carbide cutting tool according to an embodiment of the present invention will be specifically explained.

According to the usual powder metallurgy method, various raw material powders are prepared, these raw material powders are blended into a predetermined composition, mixed 24 hours a day in a ball mill, and after drying, 10 kg/
In the production of a surface-coated WCC cemented carbide cutting tool of the present invention (hereinafter referred to as the coated tool of the present invention), the powder compact is press-molded at a pressure of 20 to 50%.
in a nitrogen atmosphere at a predetermined pressure within the range of 1 torr.
Raised to a predetermined temperature within the range of 200 to 1400°C,
After raising the temperature, the atmosphere is changed to vacuum, and sintering is carried out under the conditions of holding at this raised temperature for 1 hour.On the other hand, in the production of conventional surface coated mwcx cemented carbide cutting tools (hereinafter referred to as conventional coated tools), The first coated tool was sintered under the same manufacturing conditions as the coated tool of the present invention except that the heated atmosphere was a vacuum.
Producing a WCW cemented carbide substrate having the component composition shown in the table and with or without a surface softening layer,
Subsequently, coating layers having the compositions and average layer thicknesses shown in Table 1 are formed on the surfaces of the various WCC cemented carbide substrates obtained as a result using a conventional chemical vapor deposition method, thereby forming coating layers according to the present invention. Covered tools 1-12 and conventional coated tools 1-
5 were produced respectively.

Next, the above-mentioned coated shells of the present invention (1) to 12 and 12 were prepared.

Regarding coated tools 1 to 5, Workpiece 11SNCM439 (hardness: He 280).

Cutting speed: 400m/min.

Feed: 0.3mm/rev.

Depth of cut: 2M.

Open when cutting: 15 minutes.

A continuous high-speed cutting test was conducted under the following conditions, and the flank wear width of the cutting edge was measured after the test. The measurement results are also shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, coated tools 1 to 12 of the present invention all exhibit excellent plastic deformation resistance and wear resistance, and can be used continuously even after the test. Conventional coated tools 1 to 5 all had abnormal wear on their cutting edges due to plastic deformation, and their service life ended in a short period of time.

As mentioned above, the surface-coated WCC cemented carbide cutting tool of the present invention has excellent plastic deformation resistance and wear resistance, so it is suitable for high-speed cutting that requires these properties. When used, it exhibits excellent cutting performance over an extremely long period of time.

Claims (2)

[Claims] (1) Ti on the surface of the tungsten carbide-based cemented carbide substrate.
A surface-coated tungsten carbide formed by forming a coating layer consisting of carbides, nitrides, and oxides, solid solutions of two or more of these, and a single layer or a multilayer of two or more of aluminum oxide. In a cutting tool made of base cemented carbide, the interior of the base is composed of components 4a, 5a, and 6 of the periodic table as dispersed phase forming components.
NaCl-type crystal structure compound consisting of carbides, nitrides, and carbonitrides of Group A metals, and solid solutions of two or more of these: 2 to 20%; Co or Co and Ni as binder phase forming components: 1.5
~2.9%, and the remainder substantially consists of tungsten carbide as a dispersed phase forming component and unavoidable impurities, and a part of the surface portion of the base body. Or, the entire body contains Co, or Co and Ni: 4 to 20%, over a depth of 2 to 100 μm from the surface of the substrate, with the remainder consisting essentially of tungsten carbide and unavoidable impurities. %), and the content of Co or Co and Ni is 210 to 500% higher than the content of Co or Co and Ni inside the base. Surface-coated tungsten carbide-based cemented carbide cutting tool for high-speed cutting. (2) Ti on the surface of the tungsten carbide-based cemented carbide substrate
A surface-coated tungsten carbide formed by forming a coating layer consisting of carbides, nitrides, and oxides, solid solutions of two or more of these, and a single layer or a multilayer of two or more of aluminum oxide. In a cutting tool made of base cemented carbide, the interior of the base is composed of components 4a, 5a, and 6 of the periodic table as dispersed phase forming components.
NaCl-type crystal structure compound consisting of carbides, nitrides, and carbonitrides of Group A metals, and solid solutions of two or more of these: 2 to 20%; Co or Co and Ni as binder phase forming components: 1.5
~2.9%, and further contains free carbon: 0.02~0.4% as a dispersed phase forming component, with the remainder essentially consisting of tungsten carbide as a dispersed phase forming component and unavoidable impurities. The substrate is made of a tungsten carbide-based cemented carbide having a composition, and a part or the entire surface of the substrate is coated with Co, or Co and Ni: 4 to 20 μm to a depth of 2 to 100 μm from the surface of the substrate. %, with the remainder consisting essentially of tungsten carbide and unavoidable impurities (wt%), and the content of Co or Co and Ni is greater than that of Co or Co and Ni inside the substrate. A cutting tool made of a surface-coated tungsten carbide-based cemented carbide for high-speed cutting, characterized in that the surface-coated tungsten carbide-based cemented carbide layer is comprised of a surface softening layer that is 210 to 500% larger than its content.