JPS6213430B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface-coated cutting tool that has excellent thermal shock resistance and high-temperature strength, and has low reactivity with cast iron, and is particularly suitable for use in high-speed cutting of cast iron, which requires these properties. It is. In recent years, various research and development efforts have been made to enable high-speed cutting of cast iron, and the transition to high-speed cutting of these materials is steadily being achieved, both by increasing the rigidity of machine tools and improving cutting tool materials. Yes, at the moment
One of the goals is stable cutting at a cutting speed of 300 m/min. This cutting speed is achieved by using an alumina-based sintered material that exhibits excellent oxidation resistance against the heat generated during high-speed cutting, has low chemical reactivity with cast iron, and contains alumina as a main component and has a small coefficient of friction. It was established that this can be achieved by making improvements to machine tools to enable high-speed cutting, on the premise that the machine is used as a cutting tool. However, although alumina has low reactivity with cast iron, it does not have sufficient thermal shock resistance or high-temperature strength, so cutting tools made of the alumina-based sintered material can stably cut cast iron at a cutting speed of 300 m/min. At present, it is extremely difficult to cut it. Therefore, from the above-mentioned viewpoint, the present inventors developed a cutting tool suitable for high-speed cutting of cast iron, that is, a cutting tool that has excellent thermal shock resistance and high-temperature strength, and has low reactivity with cast iron. As a result of conducting research to develop this, we found that on the surface of a sintered substrate containing silicon nitride (hereinafter referred to as Si ₃ N ₄ ) as the main component,
A single layer or a multilayer of two or more of titanium nitrides, carbonitrides, and carbonitrides, and if necessary, α-alumina (hereinafter referred to as Al ₂ O ₃₎ as the top layer. A surface-coated cutting tool consisting of a coating layer formed with
When used for cutting cast iron at high speeds above,
Si ₃ N ₄ has a small coefficient of thermal expansion, that is, it has excellent thermal shock resistance and high-temperature strength, and when forming the coating layer, nitrogen is especially Since it is well diffused into the coating layer, the adhesion strength of the coating layer to the surface of the sintered substrate is significantly improved, and furthermore, the coating layer has low chemical reactivity with cast iron. Together, they have found that it exhibits extremely superior cutting performance over a long period of time. This invention was made based on the above knowledge, and contains 90% by weight or more of Si ₃ N ₄ .
_Titanium nitride, _carbonitride , and carbonitride (hereinafter, respectively
(denoted as TiN, TiCN, and TiCNO)
A single layer of seeds or a multilayer of two or more seeds, and if necessary, a coating layer consisting of ₃ layers of Al ₂ O as the top layer with a thickness of 0.5 to 10μ
The present invention is characterized by a surface-coated cutting tool for high-speed cutting of cast iron formed with a layer thickness of m. In addition, in the surface-coated cutting tool of this invention,
The reason for limiting the Si ₃ N ₄ content of the sintered substrate to 90% by weight or more is that if the content is less than 90% by weight, Si ₃ N ₄
This is due to the fact that it is not possible to secure the excellent properties of , namely excellent thermal shock resistance and mechanical strength at high temperatures, and
The reason why the thickness of the coating layer is limited to 0.5 to 10 μm is because a layer thickness of less than 0.5 μm cannot completely block the effect of cast iron, which is the work material, on the sintered base. The sintered substrate reacts with the sintered substrate, and the wear of the sintered substrate is accelerated.
This is based on the reason that when the layer thickness exceeds m, the toughness of the tool decreases. Furthermore, the sintered substrate in the surface-coated cutting tool of the present invention contains 10% by weight of Si ₃ N ₄ as a main component.
Magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), aluminum nitride (AlN), silicon oxide (SiO ₂ ), oxide Calcium (CaO), sodium oxide (NaO), Ni,
The sintered substrate contains one or more of Co, Fe, Ge compounds, rare earth metal compounds, transition metal compounds, etc., and preferably has an average particle size of about 0.5 to It is best to use raw material powder with a diameter of 4 μm and manufacture it by hot pressing or high-temperature isostatic pressing.As a result, a product with a theoretical density ratio of 98% or more is obtained, so it has high mechanical strength and reliability. This results in a high level of performance. Further, the coating layer in the surface-coated cutting tool of the present invention is preferably formed by a normal chemical vapor deposition method, and the coating layer formed by the chemical vapor deposition method is formed from a sintered substrate during chemical vapor deposition as described above. Since the diffusion phenomenon of nitrogen occurs in the coating layer, the adhesion strength is higher and the wear resistance is higher than that of a coating layer formed by physical vapor deposition. Next, the surface-coated cutting tool of the present invention will be specifically explained using examples. Example 1 As raw material powders, 98.5% by weight of Si ₃ N ₄ powder, 1% by weight of MgO powder, and 0.5% by weight of Al ₂ O ₃ powder, each having an average particle size of 1.5 μm, were mixed in a wet method. After pulverizing and drying, a sintered material was produced by hot pressing at a temperature of 1700° C. and a pressure of 200 kg/cm ² . The resulting sintered material had a theoretical density ratio of 98.5% and a transverse rupture strength of 100 Kg/mm ² . Next, a sintered substrate (cutting chip) of CIS standard SNGN432 type was cut out from the above sintered material, and after grinding, it was charged into a metal reaction tube of an externally heated chemical vapor deposition device, and TiCl ₄ was heated at a temperature of 1050°C. A mixed gas consisting of 2% by volume, H ₂ : 90% by volume, N ₂ : 7% by volume, and ₁ % by volume of Co was introduced for 3 hours to form TiC _0.2 N _0.7 on the surface of the cutting _chip . Average layer thickness with a composition _of O _0.1 :
A coating layer of 3 μm was formed, and then a mixed gas consisting of 2% by volume of AlCl ₃ , 95% by volume of H ₂ and 3% by volume of CO ₂ was introduced in the same chemical vapor deposition apparatus at a temperature of 1000°C for 2 hours. and further on the coating layer.
A surface-coated cutting tool of the present invention was manufactured by forming a coating layer consisting of Al ₂ O ₃ with an average layer thickness of 2 μm. Next, regarding the surface-coated cutting tool of the present invention obtained as a result, and the above-mentioned sintered substrate without the formation of a coating layer (hereinafter referred to as a comparative cutting tool), the following results were obtained: Work material: FC-25 (Hardness _HB : 180) , Cutting speed: 350m/min, Feed: 0.3mm/rev., Depth of cut: 2mm, A high-speed continuous cutting test was conducted on cast iron under the following conditions, and the cutting time until the flank wear width of the cutting edge reached 0.3mm was measured. This was taken as the cutting life time. As a result, the above-mentioned surface-coated cutting tool of the present invention has a
The comparative cutting tool had a cutting life of only 2 minutes, whereas the comparative cutting tool had a cutting life of only 2 minutes. Example 2 Raw material powder has an average particle size of 1 μm
Si ₃ N ₄ powder, 0.5 μm Al ₂ O ₃ powder, 1.2 μm
Y ₂ O ₃ powder, 0.7 μm SiO ₂ powder, 0.5 μm
CaO powder, 1.2 μm Ni powder, 1.2 μm Co powder, 2 μm Fe powder, 2 μm GeO ₂ powder,
1.5 μm La ₂ O ₅ powder, 1 μm TiN powder,
1.2 μm TiC _{0.5 N 0.5} powder, 1 μm ZrO ₂ powder, 1.2 _μm HfN powder, 1 μm WC powder,
1.2μm TaN powder, 1.2μm NbN powder,
0.2μm MgO powder, 1.0μm ZrN powder, 0.9μm
μm TiO _0.8 N _0.2 powder and 1.2 μm _{TiB 2 powder}
Prepare powders, and add each of these raw powders to the first
It is blended with the composition shown in the table, mixed and ground under normal conditions in a wet process, dried, and then subjected to hot press treatment (indicated by HP) under the conditions also shown in Table 1, or in a nitrogen atmosphere. Temperature: 1700
Theoretical density ratio by sintering at ℃ for 30 minutes: 95
% or higher, the sintered materials are produced by high temperature isostatic pressing (indicated by HIP) under the conditions shown in Table 1, and then these sintered materials are molded into the CIS standard SNGN432 type. After grinding into a sintered substrate (cutting chip), a part of it is charged into a metal reaction tube of an externally heated chemical vapor deposition device, and under normal conditions,
Each

【table】

[Table] Surface-coated cutting tools 1 to 18 of the present invention were manufactured by forming single or multilayer coating layers having the compositions and average layer thicknesses shown in Table 1. In addition,
The surface-coated cutting tools 1, 6, 12 of the present invention, and
Comparative cutting tools 1 to 4 are sintered substrates having no coating layer formed thereon, and only the third layer, which is the uppermost layer, of the surface-coated cutting tool 8 of the present invention was formed by the ion plating method. Next, regarding the surface-coated cutting tools 1 to 18 of the present invention and comparative cutting tools 1 to 4 obtained as a result,
A high-speed continuous cutting test of cast iron was conducted under the conditions shown in Example 1 above, and the cutting life time was measured. These measurement results are also shown in Table 1. From the results shown in Table 1, it is clear that the surface-coated cutting tools 1 to 18 of the present invention all exhibit relatively long cutting life times compared to comparative cutting tools 1 to 4. As mentioned above, the surface-coated cutting tool of the present invention has excellent thermal shock resistance and high-temperature strength of Si ₃ N ₄ , high adhesion strength of the coating layer to the sintered substrate surface, and cast iron as the work material of the coating layer. Due to its low chemical reactivity to the steel, it exhibits excellent cutting performance for high-speed cutting of cast iron.

Claims (1)

[Claims] 1. A single layer or two types of titanium nitrides, carbonitrides, and carbonitrides on the surface of a sintered substrate containing 90% by weight or more of silicon nitride. A surface-coated cutting tool for high-speed cutting of cast iron, which is formed by forming the above multilayer coating layer with a layer thickness of 0.5 to 10 μm. 2. A single layer or a multilayer of two or more of titanium nitrides, carbonitrides, and carbonitrides on the surface of a sintered substrate containing 90% by weight or more of silicon nitride, A surface-coated cutting tool for high-speed cutting of cast iron, which has a coating layer consisting of the uppermost α-alumina layer with a layer thickness of 0.5 to 10 μm.