JPH0547632B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coated hard alloy, and particularly to a sintered hard alloy used as a base material for the coated hard alloy. In recent years, cutting processes have become more efficient, and tool materials that are suitable for high-speed cutting and high-feed cutting are required. Coated tools are available in which the surface of a hard material body is coated with a single layer or multiple layers of TiC, TiN, aluminum oxide, etc. However, the hard material that is the base material of the TiC-based cermet, TiN-based cermet, or coated tool mentioned above contains many iron group metals and uses this as a binder phase, so it cannot be used for heavy cutting such as high-speed cutting or high-feed cutting. When the temperature of the cutting edge increases, the hard material that is the base material of the cermet or coated tool will have a short life due to plastic deformation and chemical reaction. Particularly in the case of coated tools, no matter how hard or wear-resistant a coating layer is formed on the surface of the hard material that is the base material of the tool, if the hard material has the above-mentioned defects, it will not work. Unable to fully demonstrate the performance of the period. Ceramic tools made mainly of aluminum oxide are also used as materials with little plastic deformation or chemical reactions at high temperatures, but these have low strength and are also susceptible to thermal shock due to low thermal conductivity. It lacks reliability and its range of use is limited. The present invention has been made in view of the above-mentioned problems.The present invention consists of a hard alloy that is a base material of a hard alloy tool having a coating layer, and a binder phase of a hard alloy that is a base material of a hard alloy tool that has a coating layer is composed of tungsten and a small amount of iron group metal, and the base material is sintered. The objective is to provide a coated hard alloy that is suitable for heavy cutting such as high-speed cutting and high-feed cutting, which not only has good properties but also prevents plastic deformation or chemical reactions at high temperatures, increases tool life, and reduces production costs. be. The present invention uses tungsten carbide in a weight ratio of 10 to 95
%. Titanium carbide 2-80%. A mixture or intercompound of 2-80% titanium nitride and a metallic phase of tungsten is present at 0.1-10%, iron. cobalt. The base material is a sintered hard alloy containing 5% or less of one or more of the iron group metals of Nickel and 0.1 to 15% of nitrogen, and a part or all of the surface of the base material is
It is a coated hard alloy coated with 1 to 20μ of one or more of TiC.TiN.TiCN.TiCNO and Al ₂ O ₃ . Next, the sintered hard alloy that is the base material of the above-mentioned coated hard alloy will be described. Tungsten carbide 10~95wt% and titanium carbide 2
A mixture or intercompound of ~80wt% nitrogen and titanium 2~80wt% and iron. Nickel. Green compact containing 5wt% or less of iron group metals such as cobalt
³ Heating at 1300°C to 1800°C in a vacuum of 3 mmHg to denitrify part of the titanium nitride, and then TiN _1-X
The tungsten carbide is decarburized to precipitate tungsten, and the tungsten or the tungsten and a small amount of the iron group metal constitute the binder phase of the sintered hard alloy, thereby preventing plastic deformation during heavy cutting. Alternatively, the hard alloy with low chemical reaction and high strength can be obtained using conventional equipment that does not require special equipment and is advantageous in terms of cost. The reasons for limiting the above-mentioned sintered hard alloy will be described below. Tungsten carbide is essential as it decarburizes and precipitates tungsten; if its content is less than 10 wt%, the desired tungsten will not precipitate and therefore the alloy will not exhibit the desired toughness;
It becomes unsuitable as a base material for coated tools, and if it exceeds 95 wt%, there will be a corresponding insufficient amount of titanium nitride, making it difficult for tungsten to precipitate, making it impossible to obtain sufficient base material strength. Titanium carbide reacts with tungsten and titanium nitride during sintering to form TiCN or (W.Ti).
Forms CN to promote sintering, but the amount is 80wt
% or less than 2wt%, sinterability will deteriorate. Titanium nitride is also essential in this alloy because it denitrides and combines with the carbon of tungsten carbide, resulting in the precipitation of tungsten. However, if the amount is less than 2wt%, tungsten cannot be sufficiently precipitated, and 80wt%
Exceeding this is not appropriate because the amount of tungsten carbide will be correspondingly insufficient. iron. Nickel. Iron group metals such as cobalt improve the sinterability of this alloy and at the same time form a binder phase with tungsten to strengthen the alloy, but if it exceeds 5wt%, the hardness of the base alloy may decrease. This is not preferable because the amount of plastic deformation at high temperatures increases, making it impossible to obtain the desired base material. In addition, in the composition range where the base material of this coated tool has appropriate amounts of both tungsten carbide and titanium nitride and sufficient tungsten precipitation occurs, it is not necessary to contain the iron group metal, but tungsten carbide is 80wt. %, or when the amount of tungsten precipitated is small, such as below 15wt%.
Contains 5wt% or less. Further, although nitrogen exists in the alloy as nitrides and carbonitrides, it is denitrified during sintering, and the lower limit of the amount of nitrogen remaining in this alloy is set to 0.1 wt%. In addition,
Below this value, the toughness of the alloy decreases,
If it exceeds 15 wt%, the composition or sintering conditions according to the present invention will result in very little tungsten precipitation, making it unsuitable as a binder phase. We believe that these reasons are largely influenced by the properties of nitrides, similar to the fact that TiN-based cermets have better toughness than TiC-based cermets. The conventional method is to use the above-mentioned sintered hard alloy as a base material and coat part or all of its surface with a single layer or multiple layers of TiC.TiN.TiCN.TiCNO or Al ₂ O ₃ to a thickness of 1 to 20 μm. By using any method and means such as CVD or PVD, a coated hard alloy tool with excellent high temperature properties, long life and suitable for heavy cutting can be obtained. That is, when the sintered hard alloy according to the present invention is used as the base material of a coated tool, since tungsten mainly constitutes the binder phase, there is little plastic deformation when the temperature rises, and the base material has high strength. Not only will there be no peeling of the coating layer due to defects, but also
When a cemented carbide or cermet containing a large amount of iron group metal is used as a base material and is coated, a fragile double carbide phase such as the η phase is formed at the interface between the base material and the coating layer, which weakens the strength of the cutting edge. Measures to prevent these problems include increasing the amount of carbon in the base material to precipitate free carbon to suppress the formation of the η phase, and forming a cobalt-rich layer on the surface of the base material. However, if the sintered hard alloy of the present invention is used as the base material of a coated tool, the bonding phase is mainly tungsten. Therefore, even if coating treatment is performed, hardly any brittle double carbide layer is formed, and therefore it becomes a base material for coated tools with little decrease in strength. In addition, TiC and
Al ₂ O ₃ , TiN and Al ₂ O ₃ are said to be good for wear due to chemical reactions such as rake face wear, and the coating layer is selected depending on the cutting conditions, etc. However, as mentioned above, the formation of double carbides Due to the problem of adhesive strength with the base material, the conventional method was to coat TiC on the innermost layer and form the desired layer on the outside, regardless of the coating. As mentioned above, since the base material does not have a double carbide layer formed thereon, a desired layer can be formed as the innermost layer. Therefore, even with tungsten as the binder phase, it can be used as a cutting tool due to its sufficient wear resistance and high-temperature strength, but it is difficult to prevent flank wear and rake wear. However, by coating this base material, the boundary wear is greatly improved and it can be used in a wide range of cutting tools. Ta. In addition, 80wt% of titanium carbide is a component of the sintered hard alloy that is the base material of the coated tool according to the present invention.
The same effect as described above can be obtained by replacing the following with one or more carbides of Group 4a.5a.6a, or replacing 80wt% or less of titanium nitride with one or more nitrides of Group 4a.5a. Become what you have. Examples will be described below. Example 1 Commercially available tungsten carbide powder with a particle size of about 0.6μ as raw material powder, TiCN powder with a particle size of 1 to 2μ and different C/N ratios, double carbonitride powder of W and Ti with a particle size of 1 to 2μ, and a particle size of 1 to 2μ 5μ tantalum carbide. Hafnium carbide.
(Ti.Ta)CN powder (TiC/TaN=50/50) and cobalt with a particle size of 1 to 3μ. Table using nickel powder
1, mixed in a conventional wet ball mill, and formed into a mold to produce a green compact. The green compacts were held at 1600°C x 10 ^-2 mmHg for 1 hour to produce hard alloys 1 to 12 according to the present invention. The transverse rupture strength of the alloy thus obtained and the phases were identified using an X-ray diffraction device, and it was confirmed that tungsten was precipitated.
The amount of precipitated tungsten was calculated using The amount of _N2 in the alloy was also analyzed, and the results are also shown in Table 1. Witzkaas hardness is 1650Kg/
mm ² or more, transverse rupture strength is 110Kg/mm ² or more, and high hardness. It had high strength.

【table】

[Table] The hard alloys shown in Table 1 above were subjected to various coating treatments, and their transverse rupture strengths were measured. The thickness of the coating layer was examined by grinding a cross section and using an optical microscope, and the results are shown in Table 2. As a result of this test, although the transverse rupture strength decreased somewhat, the rate of decrease was extremely small compared to conventional cemented carbide and cermet.

[Table] Example 2 Invention alloy No. 2 in Table 1 (TiC + Al ₂ O ₃ coat). Same No. 5 (TiC + Al ₂ O ₃ coat). Same No. 8 (TiC
coat). Same No. 9 (TiC + Al ₂ O ₃ coat). Same No.11
From (TiC + TiCN + TiCNO + Al ₂ O ₃ coat)
We manufactured an SNG432 type throw-away chip and tested it by turning S55C coating material. The conditions are
Cutting speed V=210m/min.Depth of cut=2.0mm. Flank wear was investigated after cutting for 10 minutes at a feed rate f = 0.18 mm/r. At the same time, as comparison samples, a chip (A) made of a conventional cemented carbide coated with Al ₂ O ₃ and a TiN-containing cermet (B) were tested under the same conditions. The above results are shown in Table-3.

【table】

[Table] As shown in Table 3 above, it is clear that the coated hard alloy according to the present invention is excellent as a tool.

Claims (1)

[Claims] 1 A mixture or mutual compound of 10 to 95% tungsten carbide, 2 to 80% titanium carbide, and 2 to 80% titanium nitride and a metal phase of tungsten in a weight ratio of 0.1 to 95%
10% present, iron. cobalt. The base material is a sintered hard alloy containing 5% or less of one or more of the iron group metals of Nickel and 0.1 to 15% of nitrogen,
TiC.TiN. on part or all of the surface of the base material.
A coated hard alloy characterized by being coated with 1 _to 20μ of one or more of TiCN.TiCNO and _Al2O3 .