JPH06108258A - High strength coated sintered alloy - Google Patents

Abstract

PURPOSE:To improve the impact resistance and chipping resistance of a coated sintered alloy by constituting the coated sintered alloy of a bonding phase of specified wt.% of a hard phase imparted with a specified compressive stress and a coating film. CONSTITUTION:The surface of the matrix of a sintered alloy constituted of a hard phase of at least one kind among the carbides and nitrides of 4a, 5a and 6a group metals in the periodic table and mutlal solid solution therebetween and a bonding phase essentially consisting of Ni, Co or an Ni-Co alloy is coated with a film by chemical vapor deposition to form a coated sintered alloy. The quantity of the bonding phase is regulated to 2 to 12wt.%, the hard phase present on the surface part of the matrix is applied with 30 to 80kg/mm<2> compressive stress and the film is applied with <=20kg/mm<2> compresesive stress or is applied with no stress. In this way, the sintered alloy small in dispersion and of which quality control is easy as well, can be provided.

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.

[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.

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

[0007]

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. After studying the relationship, the optimum residual stress applied to the hard phase and the coating on the surface of the substrate differs depending on the amount of the binder phase of the substrate and the structure of the coating, and compressive stress is applied to the hard phase on the surface of the substrate. The present invention has been completed based on the finding that impact resistance and chipping resistance are remarkably excellent when the coating is in a state of no compressive stress or stress.

That is, the high-strength coated sintered alloy of the present invention comprises at least one hard phase among carbides and nitrides of metals of groups 4a, 5a and 6a of the Periodic Table and their mutual solid solutions, Ni, A coated sintered alloy in which a surface of a substrate of a sintered alloy comprising a binder phase containing Co or Ni-Co alloy as a main component is coated with a coating by a chemical vapor deposition method, the binder phase being 2 to 12% by weight. made, the rigid phase present in the surface portion of the base body is applied compressive stress 30~80kg / mm ² are either the coating under 20 kg / mm ² or less of compressive stress is applied, or stress It is an alloy that has not been added.

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. 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 binder phase constituting the substrate is less than 2% by weight of the whole substrate, the effect is weak even if the residual stress in the hard phase and the coating is controlled, and conversely it exceeds 12% by weight of the entire substrate. As the amount of the binder increases, the effect becomes weaker in the range of the residual stress that constitutes the present invention.
It was set to 12% by weight. In the case of a conventional coated sintered alloy composed of a substrate made of Co or an alloy containing Co, the binder phase has a crystal structure of a face-centered cubic structure in almost 100%. By applying an impact force by the method, the crystal structure of the binder phase on the surface of the substrate is transformed into a hexagonal crystal structure. The binder phase in the coated sintered alloy of the present invention is preferably in a state transformed to a hexagonal crystal structure as much as possible, and particularly,
The integrated phase ratio of the hexagonal bonded phase (hCP) to the bonded phase (FCC) of the face-centered cubic structure is the bonded phase present on the surface of the substrate as determined by X-ray diffractometry. 0.2
Above (h.C.P / F.C.C. ≧ 0.2),
It is preferable because it exhibits a more excellent effect of fracture resistance.

In the coated sintered alloy of the present invention, the compressive stress applied to the hard phase existing on the surface of the substrate is 30 kg /
If it is less than mm ^2, it is affected by the stress applied to the coating, but the effect on fracture resistance is weak, and conversely 80 kg /
If it exceeds mm ² , the variation is high and it becomes difficult to apply stress. The hard phase existing on the surface of the substrate is a hard phase existing on the surface of the substrate or from the surface to the inside of the substrate to a depth of about 10 μm. In other words, in the crystal X-ray diffractometer, It is the depth at which the X-ray can be transmitted and detected from the surface of the coating to the inside of the substrate.
The depth varies depending on the measurement conditions such as the X-ray target used.

The coating in the coated sintered alloy of the present invention is not particularly limited as to the coating material, but the greater the difference between the coefficient of thermal expansion of the substrate and the coefficient of thermal expansion 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,
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, the stress applied to the coating and the It is preferable because the stress imparted to the hard phase existing on the surface portion has a remarkable effect on the fracture resistance.

The coated sintered alloy of the present invention comprises a compressive stress applied to the hard phase on the surface of the substrate and a coating in a state in which neither the compressive stress applied to the coating nor the compressive or tensile stress is applied. The balance between the hard phase and the coating is important. At this time, the larger the total number of coatings, the higher the effect. Particularly, in the case of three or more layers, and more than five layers A remarkable effect is exhibited. If the total thickness of the coating is the same, the larger the total number of coatings, the more remarkable the effect of the present invention is, which is preferable.

When the compressive stress applied to the coating in the coated sintered alloy of the present invention exceeds 20 kg / mm ² , the coating peels off significantly and is substantially stable at 20 kg / m 2.
It becomes difficult to apply a compressive stress exceeding m ² to the coating.

The coated sintered alloy of the present invention is produced by applying an optimum impact force from the surface of the coated sintered alloy by the conventional CVD method and controlling the stress applied to the hard phase of the coating and the substrate surface. can do. Specifically, it can be produced, for example, by a shot peening method or a sand blast method by causing a substance having predetermined characteristics to fly and collide with the coating surface of the coating 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.

[0019]

The coated sintered alloy of the present invention balances the compressive stress applied to the hard phase existing on the surface of the substrate and the compressive stress applied to the coating or the coating not applied to the entire alloy. Has improved impact resistance, strength and fracture resistance,
In particular, the former hard phase to which a compressive stress is applied is a microcrack generated in the film during the process of forming the film, or a microcrack generated in the film by an impact force applied from the film surface to impart a stress. Of the former, the latter film acts to prevent the generation of new minute cracks during practical use, and even when new minute cracks occur in the film, the former hard The phase has a two-step barrier action that prevents the development of minute cracks 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 layers were sequentially coated to obtain a coated sintered alloy.

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 conditions consisting of the average diameter of the steel balls and the collision velocity shown in Table 2 to obtain the product of the present invention. 1 to 7 and comparative products 1 to 5 were obtained.

Inventive products 1 to 7 and comparative product 1 thus obtained
To X-rays from the surface of the coating film, the residual stress of the coating film by the X-ray diffraction method, and WC which is a hard phase existing on the surface of the substrate.
The residual stress and the crystal structure of the binder phase existing on the surface of the substrate were examined, and the results are shown in Table 2.

The residual stress was measured by using a crystal X-ray diffractometer with a Cu tube, Ni filter, 40 kv voltage and 30
Conducted with X-ray generated under the condition of mA current, WC which is a hard phase measures the stress on the (301) crystal face, and the film measures the stress on the (224) crystal face of the first layer. It was sought after.

The crystal structure of the binder phase on the surface of the substrate was measured with an X-ray generated under the conditions of 60 kv voltage and 300 mA current by using a monochromator with a rotor flex type Cu tube. C. For C, Co (1
00) surface, h. C. P is obtained by calculating the integrated intensity ratio excluding the background of each peak on the Co (100) plane.

Next, using the present invention products 1 to 7 and the comparative products 1 to 5, a work material: S48C (with four grooves), cutting speed:
A dry cutting test was carried out at 150 m / min, feed: 0.2 mm / rev, and incision: 1.5 mm, and the number of impacts caused by the groove until chipping or chipping occurred to the end of the life was calculated and listed in Table 2.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Example 2] _{4Ni-16Co-10Mo 2 C-} 14T
Using a sintered alloy substrate having an aC-56TiC (wt%) composition, a film thickness and film quality of ₂ μm TiC- ₂ μm Al ₂ O ₃ -0.5 μm Ti (C,
N) -2.5 μm Al ₂ O ₃ -0.5 μm A coated sintered alloy in which a coating of TiN was sequentially coated was prepared.

90 m of steel balls having an average diameter of 0.4 mm were formed on the surface of the coated sintered alloy by the shot peening method.
The product 8 of the present invention was obtained by colliding at a speed of / s. Invention product 8
Among them, the product 9 of the present invention was obtained by treating in the same manner as the product 8 of the present invention except that only the average diameter of the steel balls was changed to 0.5 mm.

Next, as a comparison, a comparative product 6 was obtained by treating in the same manner as the product 8 of the present invention except that only the average diameter of the steel balls in the product 8 of the present invention was 0.1 mm. Further, among Comparative Products 6, Comparative Product 7 was obtained by treating in the same manner as Comparative Product 6 except that only the average diameter of the steel balls was 0.3 mm. Further, among the comparative products 6, the comparative product 8 was prepared in the same manner as the comparative product 6 except that the film thickness and film quality of the coating was one layer of 7.5 μm TiN and the average diameter of the steel balls in the shot peening method was 0.4 mm.
Got The state of the coated sintered alloy used for the comparative product 6 without the treatment by the shot peening method was designated as the comparative product 9.

Inventive products 8 and 9 and comparative product 6 thus obtained
The hard phase of the solid solution containing TiC as the main component is the stress of the (224) plane,
The stress of the (224) plane of TiC was measured for the film (for the (224) plane of TiN in Comparative product 8) and the results are shown in Table 3 together with the results of the crystal structure of the binder phase.

Next, products 8 and 9 of the present invention and comparative products 6 to 9
Using, the material to be cut: S45C (with 4 V-grooves), cutting speed: 150 m / s, feed: 0.2 mm / rev, depth of cut: 1.5 mm, dry cutting test is performed, and chipping or chipping occurs Then, the number of impacts caused by the V-groove until the end of its life was calculated and shown in Table 3.

[0033]

[Table 3]

[0034]

The high hardness coated sintered alloy of the present invention is improved in impact resistance and fracture resistance by about 5.9 to 7.6 times as compared with the conventional coated sintered alloy which is not subjected to stress treatment. However, there is an effect that the life is also improved with this, compared to 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 quality control is easy. There is a remarkable effect that the impact resistance and the fracture resistance are improved by about 12% to 16.8 times, and the life is also improved accordingly.

Claims (3)

[Claims] 1. A main component of at least one hard phase among carbides and nitrides of metals of groups 4a, 5a and 6a of the periodic table and mutual solid solutions thereof, and Ni, Co or a Ni—Co alloy. In a coated sintered alloy obtained by coating a film by a chemical vapor deposition method on the surface of a sintered alloy substrate consisting of a binder phase,
The binder phase consists of 2 to 12 wt%, the rigid phase present in the surface portion of the base body is applied compressive stress 30~80kg / mm ² is The coating 20 kg / mm ² or less of compressive stress A high-strength coated sintered alloy characterized by being provided with or without stress. 2. The binder phase existing on the surface of the substrate is a binder phase (hC) having a hexagonal crystal structure to a binder phase (FCC) having a face-centered cubic structure determined by X-ray diffractometry. ．
P) has an integrated intensity ratio of 0.2 or more (h.C.P./F.C.
The high-strength coated sintered alloy according to claim 1, wherein C ≧ 0.2). 3. The above-mentioned film is formed by forming one film of Ti carbide, nitride, carbon oxide, oxynitride, Al oxide and mutual solid solution thereof as a multi-layer of two or more layers. A high-strength coated sintered alloy characterized in that