JPH05177413A - Covered cermet cutting tool and its manufacture - Google Patents

Abstract

PURPOSE:To provide a cover cutting tool excellent both in corrosion resistance and in chipping resistance, where a hard cover layer is provided on the surface of a cermet parent material, and its manufacture. CONSTITUTION:This covered cermet cutting tool is equipped with a hard cover layer consisting of an inner cover layer 0.5-15mum thick, which is a single layer or plural layers of compounds of Ti, Zr, or Hf provided on the surface side of a cermet parent material by chemical deposition method or Al2O3 and has tensile residual stress or does not have residual stress, and an outer cover layer 0.3-5mum thick, which is a single layer or plural layers of compounds of Ti, Zr, or Hf provided on the inner cover layer by physical deposition method, Al2O3, TiAlN, or the like and has compression residual stress.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cermet cutting tool provided with a hard ceramic coating layer on a base material of a cermet, and a method for producing the same.

[0002]

2. Description of the Related Art Cutting tools made of cermet have been used for cutting cast iron and the like, but in recent years, there has been a tendency to increase the cutting speed in order to improve cutting efficiency.
Therefore, the cutting edge temperature of the cutting tool during cutting is 800 ℃.
As described above, the deformation due to heat and flank wear are promoted, and the life of the cutting tool is significantly reduced.

In order to improve the wear resistance of the cutting tool in such a situation, as described in, for example, Japanese Patent Application Laid-Open No. 2-4972, the surface of the cermet base material of the cutting tool is subjected to an ion sputtering method or the like. It has been proposed to form a coating layer composed of a single layer or multiple layers of hard ceramics by a physical vapor deposition method or a chemical vapor deposition method such as a CVD method. However, since the coating layer formed by the physical vapor deposition method has insufficient adhesion strength with the cermet base material, peeling of the coating layer occurs in high-speed and high-feed cutting, and the effect of the coating layer cannot be sufficiently exerted. Further, in the coating layer formed by the chemical vapor deposition method, although the wear resistance is improved, the strength of the cutting edge is lowered and the chipping frequently occurs, which is not practical.

Generally, a coating layer formed by a chemical vapor deposition method has a very high adhesion strength with the base material because it is diffused with the cermet base material. Abrasion resistance is much better than that of On the other hand, however, this type of coated cutting tool has a lower cutting edge strength and poorer fracture resistance than a cermet cutting tool having no coating layer. The reason for this is that the defects during cutting occur when cracks originating from the surface of the coating layer propagate to the cermet, which is the base material, but the coating layer of hard ceramics that does not contain a binder that covers the surface is tough. This is because cracks are likely to occur because they are scarce, and because the coating layer and the base material are firmly adhered to each other, cracks that occur in the coating layer are likely to propagate to the base material.

Further, in the case of the chemical vapor deposition method, the coating temperature is usually as high as about 1000 ° C., so that the room temperature (about 20
When cooled to ℃), tensile residual stress acts on the coating layer due to the difference in thermal expansion coefficient between the cermet base material and the coating layer, and this tensile residual stress promotes the propagation of cracks. The coating layer thickness of the coating cutting tool currently generally used is in the range of about several μm to about several tens of μm, although the wear resistance increases as the coating layer thickness increases, but at the same time For the above reason, the thicker the coating layer, the larger the tensile residual stress and the lower the fracture resistance.

On the other hand, in JP-A-1-252305, a base material made of cemented carbide is coated with an inner layer such as TiC by a chemical vapor deposition method, and the inner layer is physically vapor-deposited by an ion plating method or the like. It has been proposed to improve the wear resistance of a cutting tool by coating an outer layer such as TiCN by a method. However, in the proposed coated cutting tool, the base material is a cemented carbide with excellent toughness, and it aims to improve the stable life of the cemented carbide tool for medium- and high-speed rough cutting applications. The cermet tool used for the finishing process is a brittle material whose cutting conditions are completely different from those of the cemented carbide tool.

Therefore, if it is possible to improve the fracture resistance of the hard ceramics coating layer formed on the cermet base material by the chemical vapor deposition method, in combination with the excellent abrasion resistance of this coating layer, A coated cermet cutting tool with even better cutting characteristics can be obtained. Even in the cutting process in which an intermittent load is applied, high-speed cutting or high-feed cutting process, it can be stably used or the tool life can be improved and improved.

[0008]

In view of such conventional circumstances, the present invention forms a hard ceramic coating layer on the base material of the cermet, and imparts good wear resistance to the cermet base material by the coating layer, and By providing a coating layer to improve the decrease in fracture resistance, which was inevitable in the past,
An object of the present invention is to provide a coated cermet cutting tool excellent in both wear resistance and fracture resistance, and to provide a manufacturing method thereof.

[0009]

In order to achieve the above object, in a coated cermet cutting tool in which a hard coating layer is provided on the surface of a base material made of cermet of the present invention, the hard coating layer is a base material surface. At least one of Ti, Zr, and Hf carbides, nitrides, carbonitrides, carbonates, carbonitrides, boronitrides, borocarbonitrides, and Al ₂ O _{3 provided on} the side.
Single layer or multiple layers selected from seeds with a film thickness of 0.5 to 15μ
inner coating layer having a tensile residual stress of m or no residual stress, and Ti, Zr, Hf provided on the inner coating layer
Carbide, Nitride, Carbonitride, Carbonate, Carbonitride,
And a single layer or multiple layers selected from at least one of Al ₂ O ₃ , titanium aluminum nitride, and titanium aluminum oxynitride, and an outer coating layer having a compressive residual stress of 0.3 to 5 μm. Is characterized by.

Further, in the method for producing a coated cermet cutting tool of the present invention, Ti, Zr, Hf carbides, nitrides, carbonitrides, and carbonates are formed on the surface of a base material made of cermet by a chemical vapor deposition method. A single layer or multiple layers selected from at least one kind of carbonitride, boronitride, borocarbonitride, and Al ₂ O ₃ and forming an inner coating layer having a thickness of 0.5 to 15 μm, Of the Ti, Zr, and Hf carbides on the inner coating layer by physical vapor deposition after cooling to room temperature.
Nitride, carbonitride, carbon oxide, carbonitride, and Al ₂
The outer coating layer having a thickness of 0.3 to 5 μm is formed of a single layer or multiple layers selected from at least one of O ₃ , titanium aluminum nitride, and titanium aluminum oxynitride.

[0011]

When the coating layer is formed on the base material cermet by the chemical vapor deposition method, the fracture strength of the base material cermet is usually about 5 to 9 MN / m ^3/2 , whereas the coating layer Since the breaking strength of Al ₂ O ₃ is inferior, for example, about 4 MN / m ^3/2 , even if the coating layer is a thin film, some reduction in strength is unavoidable.

Further, the coefficient of thermal expansion of the base material cermet is usually about 6.5 to 7.5 × 10 ^-6 K ^-1 , whereas
The thermal expansion coefficient of the coating layer is about 7.6 × 10 ⁻⁶ for TiC, for example.
Since K ⁻¹ and Al ₂ O ₃ are equal to or higher than about 7.9 × 10 ⁻⁶ K ⁻¹ , the coating temperature when forming the coating layer by the chemical vapor deposition method is about 1000 ° C. to room temperature after forming the coating layer. When cooled down, tensile stress is generated in the coating layer. Since this stress usually exceeds the breaking strength of the coating layer, the average spacing of 100 to 40 is applied to the coating layer.
A crack of 0 μm occurs, and part of the stress is released, or the total stress is released depending on conditions. However, usually, a strain of about 0.5 to 1.0 GPa remains in the coating layer, which promotes the propagation of cracks during cutting.

Therefore, in the present invention, the compressive stress of about 1.5 to 2.0 GPa generally remains in the hard ceramic coating layer formed by the physical vapor deposition method such as the ion plating method. Providing an outer coating layer having a compressive residual stress formed by physical vapor deposition on an inner coating layer having a tensile residual stress or no residual stress formed on a base material by a chemical vapor deposition method as described above. Thus, the tensile residual stress of the inner coating layer was canceled so that an appropriate compressive stress remained in the entire coating layer.

Specifically, T is formed on the surface of the base material of the cermet.
It consists of a single layer or multiple layers such as iC and Al ₂ O ₃ and has a film thickness of 0.5.
Forming an inner coating layer of ˜15 μm by chemical vapor deposition,
After the whole is cooled to room temperature and cracks are generated in the inner coating layer, a physical vapor deposition method is used to form a single layer or multiple layers of TiN, TiCN, etc. on the inner coating layer, and the film thickness is 0.3 μm or more. If the outer coating layer is formed, it can be confirmed by X-ray diffraction that the residual stresses of the inner coating layer and the outer coating layer cancel each other out, resulting in residual compressive stress in the entire coating layer.
It was also found that the residual compressive stress is preferably in the range of 0.2 to 2.0 GPa.

By adjusting the residual stress of the inner coating layer and the outer coating layer in this manner, it becomes possible to improve the fracture resistance of the coating layer, and as a result, good adhesion to the cermet base material and excellent adhesion are obtained. It was possible to obtain a coated cermet cutting tool in which the wear resistance was maintained and at the same time, the fracture resistance and chipping resistance of the cutting edge during cutting were greatly improved.
However, if the film thickness of the outer coating layer exceeds 5 μm, the total film thickness becomes too thick, so that the improvement in fracture resistance is reduced, so that the film thickness of the outer coating layer is in the range of 0.3 to 5.0 μm. preferable.

[0016]

[Example] I having a chip shape of model number CNGN432
A base material made of SOPET cermet was prepared, and a single-layer or multi-layer inner coating layer shown in Table 1 was formed on the surface of the base material by a known CVD method under normal conditions, and the whole was cooled to room temperature. The residual tensile stress of the inner coating layer was measured by X-ray diffraction. Next, a single-layer or multiple-layer outer coating layer shown in Table 1 was formed under ordinary conditions on the inner coating layer by a known physical vapor deposition method, and the compressive residual stress of the entire coating layer was similarly measured.

[0017]

[Table 1] Inner coating layer and film thickness Outer coating layer and film thickness Inner coating layer Sample material of the entire coating layer → (μm) → Outer (μm) Tensile residual stress Compressive residual stress 1 * None None None None 2 * TiCN / Al ₂ O ₃ None 0.3GPa −0.3GPa 10.0 5.0 3 * TiCN / Al ₂ O ₃ TiAlN 0.3GPa 0GPa 10.0 5.0 0.2 4 * TiCN / Al ₂ O ₃ TiCN / TiN 0.3GPa 1.7GPa 10.0 5.0 4.0 2.0 5 * TiCN / Al ₂ O ₃ TiCN / TiN 0.35GPa 1.4GPa 10.0 6.0 2.0 3.0 6 * ZrN TiCN / TiN 0GPa 1.1GPa 0.3 1.0 1.0 7 HfC / Al ₂ O ₃ TiCN / TiN 0.3GPa 1.4GPa 10.0 5.0 2.0 3.0 8 ZrN / HfCN TiCN / TiN 0GPa 1.2GPa 0.3 0.2 1.0 1.5 9 TiCN / Al ₂ O ₃ TiAlN 0.3GPa 0.2GPa 10.0 5.0 0.3 10 TiCN / TiBCN / TiBN / Al ₂ O ₃ HfCO / TiAlNO 0.3GPa 0.2GPa 6.0 2.0 2.0 5.0 0.1 0.2 11 TiC / TiCO / Al ₂ O ₃ ZrCNO / ZrN 0.3GPa 1.2GPa 9.5 0.5 0.5 2.0 3.0 (Note) Samples 1 to 6 marked with * are comparative examples (same below).

Using each of the obtained coated cermet cutting tools, a cutting test was performed under the following cutting conditions to evaluate the cutting performance, and the results are shown in Table 2. Wear resistance Work material: SCM415 Cutting speed: 250 m / min. Delivery: 0.3 mm / rev. Depth of cut: 1.5 mm Cutting time: 20 min. Fracture resistance Work material: SCM435 grooved material (4 grooves in the longitudinal direction at equal intervals on the outer circumference) Cutting speed: 100 m / min. Sending: 0.15-0.25 mm / rev. Depth of cut: 2.0 mm Cutting time: 0.5 min.

[0019]

[Table 2]

From the comparison of Samples 1 and 2, abrasion resistance is improved but chipping resistance is lowered only by providing the coating layer by the chemical vapor deposition method. In Sample 3, the outer coating layer is thin, so that sufficient compression is achieved. Residual stress cannot be obtained, resulting in poor fracture resistance. In Samples 4 and 5, the outer coating layer or inner coating layer is too thick, so improvement in fracture resistance is not sufficient, and in Sample 6, the inner coating layer is too thin. Therefore, it is understood that the wear resistance is poor. On the other hand, in Samples 7 to 11 of the examples of the present invention, it can be seen that an appropriate compressive residual stress remains in the coating layer, and both wear resistance and fracture resistance are improved.

[0021]

According to the present invention, as a coating layer on the cermet base material, an inner coating layer having a suitable tensile residual stress formed by a chemical vapor deposition method, and a physical vapor deposition method on the inner coating layer. Since it is laminated with the outer coating layer having a compressive residual stress formed by, the inner coating layer has excellent adhesion strength to the cermet base material and excellent compressive stress remains in the entire coating layer, resulting in excellent wear resistance. It is possible to provide a coated cermet cutting tool which has the property of improving fracture resistance at the same time.

Therefore, according to the coated cermet cutting tool of the present invention, cutting conditions which are difficult to apply to the conventional cermet cutting tool, for example, intermittent load such as milling and turning of grooved material are applied. Even in cutting, high-speed cutting or high-feed cutting, the tool life will increase,
It can be used stably.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akinori Kobayashi 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works

Claims (3)

[Claims] 1. A coated cermet cutting tool in which a hard coating layer is provided on the surface of a base material made of cermet, wherein the hard coating layer is a carbide, nitride of Ti, Zr, or Hf provided on the surface side of the base material. At least one of carbonitride, carbon oxide, carbonitride, boronitride, borocarbonitride, and Al ₂ O ₃ .
Single layer or multiple layers selected from seeds with a film thickness of 0.5 to 15μ
inner coating layer having a tensile residual stress of m or no residual stress, and Ti, Zr, Hf provided on the inner coating layer
Carbide, Nitride, Carbonitride, Carbonate, Carbonitride,
And a single layer or multiple layers selected from at least one of Al ₂ O ₃ , titanium aluminum nitride, and titanium aluminum oxynitride, and an outer coating layer having a compressive residual stress of 0.3 to 5 μm. A coated cermet cutting tool characterized by. 2. The coated cermet cutting tool according to claim 1, wherein a compressive stress of 0.2 to 2.0 GPa remains in the entire coating layer including the inner coating layer and the outer coating layer. 3. A Ti, Zr, Hf carbide, nitride, carbonitride, carbon oxide, carbonitride, boronitride, borocarbonitride on a surface of a base material made of cermet by a chemical vapor deposition method. And an inner coating layer having a thickness of 0.5 to 15 μm, which is a single layer or multiple layers selected from at least one of Al ₂ O ₃ and is cooled to room temperature, and then subjected to physical vapor deposition to form an inner layer. On top of the coating layer, Ti, Zr, Hf carbides, nitrides, carbonitrides, carbonates, carbonitrides, and Al ₂ O ₃ ,
A method for producing a coated cermet cutting tool, which comprises forming an outer coating layer having a film thickness of 0.3 to 5 μm with a single layer or multiple layers selected from at least one of titanium aluminum nitride and titanium aluminum oxynitride. .