JPH06173014A - High strength coated sintered alloy - Google Patents

Abstract

PURPOSE:To apply stress to a hard phase and a coating on the surface part of a substrate in a sintered allay with a good balance and to improve its impact resistance and chipping resistance by applying compressive stress with a speci fied depth distribution to the hard layer on the surface part of the substrate from the surface of the substrate toward the inside. CONSTITUTION:This coated sintered allay is formed by coating the surface of a substrate constituted of a sintered alloy containing 84 to 98wt.% hard phase of at least one kind among the carbides and nitrides of 4a, 5a and 6a group metals and the mutual solid solution thereamong and a bonding phase essentially consisting of Co or an Ni-Co allay with a film. The surface of the substrate of the coated sintered allay is bombarded with flying substance such as steel balls to apply compressive stress from the surface of the substrate to a depth of at least 40mum inside. This compressive stress is gradually increased from the surface toward the inside, and the maximum compressed stress is attained on the surface part of the substrate at the inside of 2 to 20mum from the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength coated sintered alloy having excellent impact resistance and chipping resistance, and particularly suitable for a tool represented by a cutting tool or a wear-resistant tool. It is about.

[0002]

2. Description of the Related Art A coated sintered alloy obtained by coating a surface of a substrate of a sintered alloy represented by cemented carbide and cermet with a highly hard coating is roughly classified by a chemical vapor deposition method (CVD method). There are coated sintered alloys and coated sintered alloys by physical vapor deposition (PVD method). In these coated sintered alloys, residual stress based on the manufacturing conditions or residual stress based on the difference in thermal expansion coefficient between the material of the coating and the material of the base remains on the surface of the coating and the base.

As a representative example of the relationship between the residual stress inherent in the coated sintered alloy and various characteristics of the coated sintered alloy, Yamamoto et al., Journal of the Japan Institute of Metals 50 (3).
(1986) 320 and JP-A-64-31972. In addition, the heat treatment of Yoshikawa et al., 29, has been investigated as to the residual stress of the coated sintered alloy and its distribution.
There is (1) (1989) 9.

[0004]

According to Yamamoto et al., Journal of the Japan Institute of Metals, 50 (3) (1986) 320, the coated sintered alloy by the CVD method contains tungsten carbide, which is a hard phase present on the surface of the substrate, and tungsten carbide. It is described that tensile stress acts on both of the titanium nitride films. And
In Yamamoto et al.'S reference, the coated sintered alloy by the CVD method is
It has been described that the flexural strength and fracture toughness values are extremely reduced as compared with a sintered sintered alloy obtained by the PVD method or an uncoated sintered alloy.

Further, Japanese Patent Laid-Open No. 64-31972 discloses a coating obtained by applying a compressive stress of 50 kg / mm ² or more to the hard phase and / or the coating existing on the surface of the substrate of the coated sintered alloy by the CVD method. Sintered alloys are described. The coated sintered alloy of the publication is present in the hard phase and / or the coating on the surface of the substrate by applying an impact force from the coating surface of the coated sintered alloy by the conventional CVD method by the shot peening method or the sandblast method. This is an excellent alloy in which tensile stress is used as compressive stress and the strength of the coated sintered alloy is remarkably increased. However, depending on the amount of binder phase of the substrate, the thickness of the coating, the quality of the coating and the multilayer coating, the strength may be reversed. There is a problem that it will decrease.

Furthermore, the heat treatment of Yoshikawa et al. 29 (1) (19)
89) 9, according to the coated sintered alloy by the CVD method,
It is described that an abnormal stress distribution exists only in the range of ± 0.3 μm near the interface between the substrate and the coating.

The present invention solves the above-mentioned conventional problems. Specifically, stress is applied in a well-balanced manner to both the hard phase and the coating on the surface of the substrate, and the impact resistance and resistance It is an object of the present invention to provide a coated sintered alloy capable of maintaining the maximum defectivity.

[0008]

Means for Solving the Problems The inventors of the present invention have made it possible to control the stresses inherent in the hard phase and the coating on the surface of the base body of the coated sintered alloy, and the stresses imparted to them and the performance as a cutting tool. As a result of studying the relationship, the optimum residual stress applied to the hard phase on the surface of the base and the coating differs depending on the amount of the binder phase of the base and the structure of the coating. The present invention has been completed based on the finding that impact resistance and fracture resistance are remarkably excellent by applying a compressive stress having a depth distribution from the inside to the inside of the substrate.

That is, the high-strength coated sintered alloy of the present invention comprises at least one hard phase of carbides, nitrides and mutual solid solutions of 4a, 5a and 6a metals in the periodic table in an amount of 84 to 98% by weight. % And the remaining Ni, Co or Ni-Co
A coated sintered alloy obtained by coating the surface of a substrate of a sintered alloy having a binder phase containing an alloy as a main component with a coating, and compressing the surface of the substrate at a depth of at least 40 μm from the surface of the substrate. A stress is applied, and the compressive stress of the surface portion of the substrate gradually increases from the surface of the substrate toward the inside,
The maximum compressive stress at the surface of the substrate within 2 to 20 μm from the surface of the substrate is followed by a gradual decrease to the residual stress inside the substrate.

The substrate of the coated sintered alloy of the present invention is a cemented carbide or cermet which has been publicly known and used conventionally, and specifically, for example, TiC, ZrC, HfC, V.
C, NbC, TaC, WC, Cr ₃ C ₂ , Mo ₂ C, Ti
N, ZrN, HfN, VN, NbN, TaN, Ti
(C, N), (Ti, Ta) C, (Ti, Ta, W)
C, (Ti, Ta, Nb, W) C, (Ti, Ta)
(C, N), (Ti, Ta, W) (C, N) at least one hard phase and Ni, Co, or Ni-Co alloy, or a few percent of hard phase elements and Fe. Hereinafter, it is composed of a binder phase formed as a solid solution. Of these, cemented carbide with a hard phase based on WC, or TiC or Ti
In the case of a base body composed of a cermet having a hard phase based on (C, N), the effect becomes remarkable, which is particularly preferable.

When the amount of the binder phase constituting the substrate is less than 2% by weight of the whole substrate, the effect is weak even if the stress remaining in the hard phase is controlled, and conversely, when it exceeds 16% by weight of the entire substrate. In the range of the residual stress that constitutes the present invention, the effect is weakened, so the amount of the binder phase of the substrate is set to 2 to 16% by weight. Therefore, the hard phase amount is 84 to 98 wt% because it has a relative relationship with the binder phase amount.

In addition, the depth of the substrate surface portion, which is the distribution range of the compressive stress applied to the hard phase, in other words, the inside of the substrate applied in the depth direction from the surface of the substrate to the inside of the substrate. When the residual stress range is different, that is, the compressive stress distribution range is less than 40 μm from the surface of the substrate, the fracture resistance is significantly deteriorated. Therefore, it is defined as at least 40 μm from the surface of the substrate. is there. The range of compressive stress distribution on the substrate surface is 100μ from the substrate surface
Since it is very difficult to apply the resin to the inside of m, it is particularly preferable that the distance from the surface of the substrate is 50 to 100.
The depth to the inside of μm is preferable.

Further, in the position where the maximum compressive stress is present on the surface of the substrate, that is, in the inside where the maximum position of the compressive stress is less than 2 μm from the surface of the substrate, the fracture resistance is remarkably lowered and exceeds 20 μm from the substrate surface. Since it is difficult to apply inside, it is defined as 2 to 20 μm from the surface of the substrate. The maximum stress at this time is 80 to 250 kg /
It is preferably mm ² .

The coating material in the coated sintered alloy of the present invention is not particularly limited as to the coating material, but the larger the difference between the thermal expansion coefficient of the substrate and the thermal expansion coefficient of the coating material, the higher the effect. Specifically, for example, the periodic table 4a, 5a,
Carbides, nitrides, oxides, borides, Si of 6a group metals
Carbides, nitrides, Al oxides, nitrides and their mutual solid solutions, diamond, diamond-like carbon,
Cubic boron nitride may be mentioned. The thickness of this coating is 20 μm because it tends to peel off if it is made too thick.
In particular, when the thickness is 10 μm or less, variations are small, performance is stable, and excellent effects are obtained, which is preferable.

Further, the coating material is Ti carbide, nitride,
A hard phase existing on the surface portion of the substrate when it is composed of one or more of carbonates, oxynitrides, oxides of Al and mutual solid solutions thereof and is formed of multiple layers of two or more layers. It is preferable because the stress imparted to the steel has a remarkable effect on the fracture resistance. Depending on the film thickness of the coating film, especially the distribution range of the compressive stress applied to the hard phase on the surface of the substrate, the maximum position of the compressive stress, and the balance relationship with the maximum compressive stress value are important. It is preferable, or if the film thickness is constant, that the larger the total number of coating films is, the higher the effect is, and it is preferable that a multilayer having 3 or more layers, and further a multilayer having 5 or more layers exhibit a more remarkable effect. The residual stress of the coating film at this time is 20 kg / mm ² or less,
It is preferably in a zero state in which no compressive stress or residual stress of 0 kg / mm ² or less is applied.

The coated sintered alloy of the present invention is produced by applying an optimum impact force from the surface of the coated sintered alloy prepared by the conventional CVD method or PVD method to control the stress applied to the hard phase on the surface of the substrate. Can be made. In particular,
For example, a shot peening method or a sand blasting method can be used to produce a material having predetermined characteristics by causing the material having predetermined characteristics to fly and collide with the coating surface of the coated sintered alloy at a predetermined speed.

Further, the method for producing the coated sintered alloy of the present invention will be described in detail. The substance having a predetermined characteristic (flying substance) that causes a flying collision from the coating surface means the density, Young's modulus, Poisson's ratio and It is a spherical substance considering the diameter, and examples thereof include a steel ball having a diameter of 0.3 to 1 mm and a cemented carbide having a diameter of 0.1 to 1 mm. The predetermined speed for flying the flying material may be, for example, 5 to 100 m / s as a guide. When the flying material is a steel ball, it is 30 to 100 m / s, and when the flying material is a cemented carbide ball. Is 5 to 60 m / s, further 60 to 100 m / s when the size of the spherical body is 0.1 to 0.4 mm in diameter, 30 to 70 m / s when the diameter is 0.4 to 0.7 mm, and 0 in diameter. In the case of 0.7 to 1.0 mm, it is preferably 5 to 40 m / s.

From another point of view, in the case of a soft flying material such as a steel ball, the speed is increased, and in the case of a hard flying material such as a cemented carbide ball, the speed is slowed, and Fine spheres are preferable as much as possible. The distribution range of the compressive stress applied to the hard phase on the surface of the substrate, the maximum position, and the maximum compressive stress value may be controlled by the size of the shape of the flying material, the hardness of the material, and the impact force. As a general guide, when the shape is increased, the hardness of the material is increased, and the impact force is increased, the distribution range, the maximum position, and the maximum compressive stress value tend to increase.

[0019]

In the coated sintered alloy of the present invention, the compressive stress imparted to the hard phase existing on the surface of the substrate enhances the impact resistance, strength and fracture resistance of the entire alloy. The distribution range and its maximum position are microcracks generated in the film during the process of film formation, or the development of microcracks in the film due to the impact force applied from the film surface to impart stress to the inside of the substrate. Acts to prevent
Even when new microcracks are generated in the coating, the latter maximum position has a two-step barrier action that prevents the microcracks from propagating inside the substrate.

[0020]

Example 1 Using a cemented carbide substrate having the composition components shown in Table 1, the surface of the substrate was coated with a film by a conventional CVD method. The film has the film thickness and film quality shown in Table 1, and has a first layer, a second layer, and a third layer on the substrate surface.
The layer and the fourth layer were sequentially coated to obtain a coated sintered alloy.

In the present invention, an impact force is applied to the coating surface of the coated sintered alloy having the constitution shown in Table 1 under the shot peening condition consisting of the spherical or columnar flying material and the collision velocity shown in Table 2. Products 1 to 10 and comparative products 1 to 3 were obtained.

The residual stress of WC, which is a hard phase existing on the surface of the substrate, was determined by X-ray diffractometry by irradiating X-rays from the coating surfaces of the inventive products 1-10 and comparative products 1-3 thus obtained. In particular, the range from the surface of the substrate where the residual stress different from the residual stress inside the substrate exists to the inside, (the distribution range of the applied compressive stress), the maximum compressive stress is applied within the range. The position (maximum position) from the surface of the substrate to the inside and the maximum compressive stress value at the maximum position were examined and are also shown in Table 2.

The residual stress was measured by using a crystal X-ray diffractometer, a V tube, a Ti filter, a voltage of 30 kv, and a pressure of 10 m.
The WC, which is a hard phase, was obtained by measuring the stress in the crystal plane of the (111) plane, which was performed by X-rays generated under the condition of the A current. The residual stress in the depth direction from the surface of the substrate to the inside is measured by the above-mentioned X-ray diffraction method while removing the lap with 1 μm diamond paste.

The compressive stress on the surface of the substrate of Products 1 to 10 of the present invention gradually increased from the surface of the substrate toward the inside, and after reaching the maximum compressive stress at the maximum position shown in Table 2, the substrate was further compressed. Gradually decreasing toward the inside of the substrate, reaching the residual stress inside the substrate.

Next, products 1 to 10 of the present invention and comparative products 1 to 3
Further, using a coated sintered alloy corresponding to the comparative product 2 not subjected to the shot peening treatment as the comparative product 4, the work material: S48C (with four grooves), the cutting speed: 150 m /
min, feed: 0.2 mm / rev, depth of cut: 1.5 m
The dry cutting test with m was performed, and the number of impacts caused by the groove until the end of the life due to chipping or chipping was obtained and the results are also shown in Table 2.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

Example 2 10Co-20TiC-10TaC-60
By using a sintered alloy substrate having a WC (wt%) composition, a coating was applied to the surface of the substrate by the conventional CVD method. The coating film had the film thickness and film quality shown in Table 3, and the surface of the substrate was sequentially coated with the first layer or the first to fifth layers to obtain a coated sintered alloy. Impact forces were applied from the coating surface of these coated sintered alloys under the shot peening conditions shown in Table 4 to obtain inventive products 11 to 15 and comparative products 5 and 6. The present invention products 11 to 15 and the comparative products 5 and 6 thus obtained were examined for residual stress distribution on the surface portion of the substrate by the same method as in Example 1 and are also shown in Table 4.

The products 11 to 15 of the present invention have the same compressive stress distribution on the surface of the substrate as the products 1 to 10 of the first embodiment.

Next, using the products 11 to 15 of the present invention and the comparative products 5 and 6, a work material: S48C (with four V grooves), a cutting speed: 150 m / s, and a feed: 0.2 mm / r.
ev, depth of cut: 1.5mm dry cutting test,
The number of impacts caused by the V-groove until the end of life due to chipping or chipping was determined and listed in Table 4.

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

The high-strength coated sintered alloy of the present invention is about 5.5 times to 16.7 times in impact resistance and fracture resistance as compared with the conventional coated sintered alloy which is not subjected to stress treatment. There is an effect that it improves, and the life is also improved accordingly. Compared with the conventional coated sintered alloy subjected to stress treatment or the coated sintered alloy outside the scope of the present invention, there is little variation and the quality control is easy. The impact resistance and fracture resistance are about 1.7 times to 4.
There is a remarkable effect that the life is improved five times and the life is also improved accordingly.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display C22C 29/02 29/16 C23C 16/30 7325-4K

Claims (3)

[Claims] 1. At least one hard phase of carbides, nitrides and mutual solid solutions of 4a, 5a and 6a metals of the periodic table, 84 to 98% by weight, and the balance of Ni, Co or NiCo alloy. In a coated sintered alloy obtained by coating a surface of a base of a sintered alloy having a binder phase as a main component, a compressive stress is applied to the surface of the base at a depth of at least 40 μm from the surface of the base. The compressive stress on the surface of the substrate gradually increases from the surface of the substrate toward the inside, and gradually decreases after reaching the maximum compressive stress on the surface of the substrate within 2 to 20 μm from the surface of the substrate. A high-strength coated sintered alloy having a residual stress inside the substrate. 2. The maximum compressive stress is 80 to 250 kg.
/ Mm² The high strength according to claim 1, wherein
Coated sintered alloy. 3. The coating comprises a single layer or a multilayer of at least one of Ti carbide, nitride, carbon oxide, nitrous oxide, Al oxide, nitride and their mutual solid solution, and The high-strength coated sintered alloy according to claim 1 or 2, wherein a compressive stress of 20 kg / mm ² or less is applied to the coating.