JPH0196084A - Surface-coated cubic boron nitride-based material sintered under superhigh pressure to be used for cutting tool - Google Patents

Abstract

PURPOSE:To obtain a cutting tool capable of maintaining high cutting performance for a long time by covering a surface of a base body of a material to be sintered under superhigh pressure contg. CBN and a bonding phase-forming component such as Co, Al, Ti, W, etc., with thin film of carbide, nitride, or carbonitride of Ti, interposing a thin film layer of metallic Ti. CONSTITUTION:The title cutting material is constituted of a base body of a CBN-based material sintered under superhigh pressure consisting of (a) 5-20vol.% at least one kind among Co, Al, Ti, W, Mo, and Ni, as bonding phase-forming component, and (b) residual vol.% CBN and inevitable impurities, and a rigid layer consisting of either one among carbide, nitride, and carbonitride of Ti, having 1-10mum mean thickness, covering the surface of the base body interposing a metallic Ti layer having 0.05-0.5mum mean thickness between the surface of the base body and said rigid layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the use of cubic boron nitride (hereinafter referred to as "cubic boron nitride") suitable for use as a cutting tool in the finishing cutting of cast iron, particularly gray cast iron, and Fe-based sintered alloys. The present invention relates to ultra-high pressure sintered materials (denoted as CBN).

[Conventional technology]

Conventionally, as described in, for example, JP-A-59-8679, Co and Al have been used as bonded phase forming components.

On the surface of a CBN-based ultra-high pressure sintered material substrate containing 5 to 20% by volume of one or more of TI, W, Mo, and Ni, with the remainder consisting of CBN and unavoidable impurities, 4a of the periodic table.

A surface-coated CBN-based ultra-high pressure sintered material coated with a hard layer consisting of a single layer or a multilayer of two or more of carbides, nitrides, and carbonitrides of group 5a and 6a metals. Attempts have been made to use it as a cutting tool for finishing cutting of cast iron and Fe-based sintered alloys.

[Problem that the invention seeks to solve]

However, in the conventional surface-covered 1cBN-based ultra-high pressure sintered material, the hard layer easily peels off, and as cutting speeds have increased due to labor saving and rationalization in recent years, this tendency has been accelerated. At present, it is difficult to stably put it into practical use as a tool.

[Means for solving problems]

Therefore, from the above-mentioned viewpoint, the present inventors focused on the conventional surface-coated CBN-based ultra-high-pressure sintered material, aimed at improving the adhesion of its hard layer, and commercialized it as a cutting tool. As a result of research to make this possible, we found that the hard layer was made of Ti.
carbides, nitrides, and carbonitrides (hereinafter referred to as T
iC, TiN.

and T1CN), and then interposing a metal T1 layer between this hard layer and the substrate surface, the adhesion of the hard layer to the substrate surface is dramatically improved. This prevents the hard layer from peeling off during high-speed finish cutting of cast iron and Fe-based sintered alloys.
They found that it exhibits excellent wear resistance over a long period of time.

This invention was made based on the above findings, and uses Co and AΩ as bonding phase forming components.

Contains one or more of Ti, W, Mo, and Nl: 5 to 20% by volume, and the remainder is CBN.
On the surface of a CBN-based ultra-high pressure sintered material base having a composition consisting of and T1CN,
The present invention is characterized by a surface-coated CBN-based ultra-high pressure sintered material for a cutting tool, which is coated with a hard layer having a predetermined average layer thickness within the range of 1 to 10 μm.

Next, in the surface-coated CBN-based ultra-high pressure sintered material of the present invention, the reason for limiting the numerical values as described above will be explained.

(a) Content of binder phase forming component If the content is less than 5% by volume, the toughness decreases and CBN
Particles become more likely to fall off, causing shedding wear.
On the other hand, if the content exceeds 20% by volume, plastic deformation is likely to occur, which accelerates wear, so the content was set at 5 to 20% by volume.

(b) Average layer thickness of metal Ti layer The metal Ti layer has the effect of dramatically improving the adhesion of the hard layer to the substrate surface as described above, but if the average layer thickness is less than 0.05 μm, the above-mentioned If the desired effect of improving the action cannot be obtained, and on the other hand, the average layer thickness exceeds 0.5 μm, the thermal conductivity will decrease and heat will become trapped at the cutting edge, making it easy to plastically deform. The average layer thickness should be set at 0.05 to 0.
．． It was set as less than 5 μm.

(e) Average layer thickness of the hard layer The hard layer has the effect of improving wear resistance, reducing abnormal wear especially at the cutting edge boundary, and improving the finished surface roughness. If the thickness is less than 1 μm, the desired effect cannot be obtained; on the other hand, if the average layer thickness is 10 μm
Since chipping (chips on the cutting edge) is likely to occur if the thickness exceeds 100 μm, the average layer thickness was set at 1 to 10 μm.

〔Example〕

Next, the surface-coated CBN-based ultra-high pressure sintered material of the present invention will be specifically explained with reference to Examples.

First, as raw material powders, CBN powder and various metal powders each having a desired average particle size within the range of 3 to 5 μm are prepared, and these raw material powders are mixed into the compositions shown in Table 1. After blending and mixing, ultra-high pressure sintering was performed under the conditions of pressure crab 50,000 atm, temperature: 1400°C, holding time = 30 minutes, resulting in a CBN-based ultra-high pressure sintered product having substantially the same composition as the blended composition. The present invention is achieved by producing a bonding material, and then using this as a base material, and forming a metal Ti layer and a hard layer on the surface thereof, both of which have the average layer thickness shown in Table 1, by the usual ion blasting method. Invention surface-coated cutting tips made of CBN-based ultra-high pressure sintered material (hereinafter referred to as invention coated cutting tips) 1 to 9 and comparative surface-coated cutting tips made of CBN-based ultra-high pressure sintered material without formation of metal Ti layer (hereinafter referred to as comparative coated cutting tips) 1 to 3 (referred to as cutting chips) were manufactured, respectively.

Next, the various coated cutting chips obtained as a result were subjected to the following steps: Work material: Fe12° Cutting speed: 60 G m/min.

Depth of cut: 0.2 Ilm.

Feed: 0.3 mm/rev.

Dry finishing cutting of gray cast iron was carried out under the condition of cutting time = 6010°, and the cutting time until a chipping occurred on the cutting edge was measured.

These results are shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, the coated cutting tips 1 to 1 of the present invention
9, the adhesion of the hard layer to the substrate surface is extremely high due to the metal Ti layer interposed between the substrate surface and the hard layer, so there is no cutting edge damage due to hard layer peeling, and the service life is shortened. On the other hand, it is clear that the comparative coated cutting tips 1 to 3, in which no metal Ti layer was formed, suffered damage to the cutting edge in a relatively short period of time and reached the end of their service life.

As mentioned above, the surface-coated CBN-based ultra-high pressure sintered material of the present invention has extremely high adhesion of the hard layer to the substrate, so it can be used as a cutting tool for high-speed finishing cutting of cast iron and Fe-based sintered alloy. The hard layer will not peel off when
It exhibits excellent cutting performance over an extremely long period of time.

Claims (1)

[Claims] Co, Al, Ti, W, Mo,
The surface of a cubic boron nitride-based ultra-high pressure sintered material substrate containing 5 to 20% by volume of one or more of Ni and Ni, with the remainder consisting of cubic boron nitride and unavoidable impurities. Through a metal Ti layer having an average layer thickness of 0.05 to less than 0.5 μm, a hard layer having an average layer thickness of 1 to 10 μm and consisting of any one of Ti carbide, nitride, and carbonitride. Surface-coated cubic boron nitride-based ultra-high pressure sintered material for cutting tools.