JPH05106060A - Surface strengthening treatment method for cermet material - Google Patents

Abstract

PURPOSE:To fill the deficient part on the surface of a cermet material with a metallic phase. CONSTITUTION:A roll-shaped electrode 14 for treatment using cobalt as material is abutted on the surface of a cermet material 10 deficient in cobalt in the surface. Direct current of 20V voltage and about 5 to 15A electric current is impressed on the space between the electrode 14 and the cermet material 10 via a Lazarenko (Phonetic) circuit as well as the electrode 14 is moved while it is abutted on the surface of the cermet material 10. The electric current is short-circuited between tungsten carbide exposed on the surface of the cermet material 10 and the electrode 14, and discharge is executed at the part deficient in cobalt. Then, cobalt in the electrode 14 is ionized by the discharge and transits to the deficient part in the cermet material 10, by which its surface repair is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for strengthening the surface of a cermet material. More specifically, the metal phase as a binder is partly lost due to electric discharge machining or wire cutting to prevent bending and tensile loads. The present invention relates to a surface repair of a cermet material which can be made stronger by previously coating a metal phase lacking portion in the cermet material having reduced strength so as to fill the metal phase.

[0002]

2. Description of the Related Art Cermet materials (heat-resistant sintered bodies) made by bonding hard-particle ceramics such as carbides, oxides, nitrides, and silicides with metal phases such as titanium and cobalt have high mechanical hardness. It has excellent wear resistance. Therefore, it is widely used in various industries as a cutting tool such as a bite tip, a trimming punch for hot forging, and a wear resistant part for harsh environments such as a rocker arm of an engine. Due to their superhardness, these cermet materials are extremely difficult to be machined such as cutting and grinding. For this reason, the processing of the cermet material is performed only by a special means using electric discharge such as an electric discharge machining method or a wire cutting method.

[0003]

By the way, although the cermet material is a high-strength composite material, it is subjected to external stress such as bending load or tensile load after being processed by the above-mentioned electric discharge machining method or wire cutting method. On the other hand, it has a serious drawback that it becomes very weak. The reason is that, for example, hard particles of tungsten carbide (WC) are replaced with cobalt.
Cermet material 10 formed by strongly bonding with (Co) metal phase
When the above-mentioned electric discharge machining or wire cutting is applied to this, as shown in FIG. 3, a part of the cobalt functioning as the binder is missing on the surface of the cermet material, and the missing parts (notches) are scattered. Is caused by. That is, when a stress such as a large bending load or a tensile load is applied to the cermet material 10 from the outside in the cermet material 10 having the defect portion on its surface, as shown in FIG. , Which grows and eventually breaks.

[0004]

It is an object of the present invention, as described above, that when the cermet material is subjected to electric discharge machining or wire cutting, the metal phase strongly binding the ceramics of the hard particles is damaged on the surface of the cermet material. In view of the drawback of unavoidably lowering the stress resistance strength, it has been proposed to suitably solve this, and a coating for compensating for the metal phase in the missing portion of the metal phase is provided. It is an object of the present invention to provide a method for modifying the surface of a cermet material, which is designed to achieve high strength.

[0005]

In order to overcome the above-mentioned problems and preferably achieve the intended purpose, a method for surface-strengthening a cermet material according to the present invention comprises hard particles such as carbides, oxides and nitrides. When ceramics of No. 1 are partly missing on the machined surface by performing various machining such as electric discharge machining or wire cutting on the cermet material formed by bonding the ceramics of the metal phase with titanium or cobalt , Contacting the surface of the cermet material with an electrode material made of a metal phase suitable for compensating for the missing metal phase, and a voltage having a potential opposite to that at the time of electric discharge machining between the electrode material and the cermet material. The electrode material and the cermet material are relatively moved while applying the electric field, and the discharge and the short circuit are repeated between them, thereby forming the material of the electrode material in the metal phase missing portion on the surface of the cermet material. Metal phase And characterized by applying coating.

[0006]

EXAMPLES Next, the method for strengthening the surface of a cermet material according to the present invention will be described below with reference to preferred examples.
The cermet material 10 shown as a side face in FIG. 1 has a surface thereof which is deficient in cobalt (Co) which is a metal phase as a binder, and tungsten carbide (WC) which is hard particle ceramics. ) Is exposed in a state where the bond is partially released. Therefore, this missing metal phase, cobalt (C
a roll-shaped processing electrode 14 made of o),
This is brought into contact with the surface of the cermet material 10. Then, a DC voltage of 20 V and a current of 5 to 15 A is applied between the electrode 14 and the cermet material 10, and the roll-shaped electrode 14 is rotated in one direction while being in contact with the surface of the cermet material 10. ..

As a circuit for applying a DC voltage to the electrode 14 and the cermet material 10, as shown in FIG. 1, for example, a Lazarenko circuit used in an electric discharge machining method is preferably used. In this Lazarenco circuit, the capacitor C ₁ is inserted in parallel with the voltage application target, so that the capacitor C ₁ is charged when the electrode 14 is in contact with the cermet material 10. However, the electrode 14
When is spatially separated from the cermet material 10, the voltage stored in the capacitor C ₁ is released at once between the two and discharged. That is, as the electrode 14 moves, a current is short-circuited between the hard particles of tungsten carbide (WC) exposed on the surface of the cermet material 10 and the electrode 14, and a metal phase of cobalt (Co) is generated. Electric discharge is performed at the defective portion. By this discharge, cobalt (Co), which is the metal phase of the roll-shaped electrode 14, is ionized and transferred to the metal phase defect portion of the cermet material 10 located in the vicinity. As described above, in the present invention, a kind of electric discharge cohesion phenomenon is utilized, so that a potential opposite to that of electric discharge machining is applied between the electrode 14 and the cermet material 10. In the embodiment, the roll-shaped electrode 14 is provided with a plus (+) and the cermet material 10 is provided with a minus (-).

With the movement of the roll-shaped electrode 14, the short circuit of the applied voltage and the discharge are repeated, and the electrode 1 is discharged at the time of the discharge.
Cobalt (Co) forming 4 is the cermet material 10
It transforms to the cobalt deficient portion on the surface of, and fills the deficient portion with the same metal phase. Therefore, as shown in FIG. 2, on the surface of the cermet material 10, the metallic phase of cobalt (Co) is coated on the defect portions (notches) formed between the tungsten carbide (WC) particles of the hard particles. It will be. For this reason, even with the cermet material 10 that has been subjected to the electric discharge machining or wire cutting, even if a large external stress such as bending load or tensile load is applied by surface repair to fill the defective portion, It is possible to improve the strength against this.

In the illustrated example, the electrode 14 is rotated and moved with respect to the cermet material 10.
You may make it move the cermet material 10 with respect to 4. Furthermore, the electrode 14 for compensating for the metal phase missing on the surface of the cermet material 10 does not necessarily have to be made of the same metal phase as the metal phase related to the missing, and may be another metal phase. Alternatively, it may be a composite material of a metal phase related to a defect and another metal phase. It is also possible to use milliV and milliA levels depending on the properties of the metal phase that also supplements the applied voltage and current.

As a practical example, this surface strengthening treatment method was carried out on a trimming punch used in a hot high-speed forging machine. This type of trimming punch uses the above-mentioned cermet material as a base material, but in the past, chipping and cornering of the corner portion were quick, and the life was about 42,000 times. However, when the trimming punch was used under the same conditions after being subjected to the surface strengthening treatment method according to the present invention, the service life was extended to about 105,000 times, 2.5 times that of the conventional one. It was confirmed that

[0011]

As described above, according to the method for surface-strengthening a cermet material according to the present invention, in a cermet material in which ceramics of hard particles such as carbide are bonded with a metal phase such as cobalt, By performing the electric discharge machining or wire cutting, even if the metal phase functioning as a binder is partially missing and the strength against bending load and tensile load is reduced, the missing part of the metal phase of the cermet material, It is possible to increase the strength by performing a coating to supplement the metal phase in advance.
Moreover, since the means is simple, the operation is extremely easy, and there is an excellent advantage that a device for carrying out the operation can be inexpensive.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an example for suitably carrying out the method for surface-strengthening a cermet material according to the present invention.

FIG. 2 is a schematic side view showing a state in which a metallic phase of cobalt is coated on a defect formed between tungsten carbide on the surface of a cermet material.

FIG. 3 is a partial plan view showing a state in which a metal phase functioning as a binder is partially missing on the surface due to electrical discharge machining or the like applied to the cermet material, resulting in spattered defects. is there.

FIG. 4 is a cross-sectional view showing a state in which, when a stress such as a large bending load is applied to a cermet material having a defective portion on its surface, the stress concentrates on the defective portion to form a crack.

[Explanation of symbols]

 10 Cermet material 12 Crack 14 Electrode WC Tungsten Carbide Co Cobalt

Claims (4)

[Claims] 1. A cermet material obtained by bonding ceramics of hard particles such as carbides, oxides, and nitrides with a metal phase such as titanium and cobalt is subjected to various processes such as electric discharge machining and wire cutting. When a part of the metal phase is missing on the processed surface, an electrode material made of a metal phase suitable for compensating the missing metal phase is brought into contact with the surface of the cermet material. Material and cermet material are applied with a voltage having a potential opposite to that at the time of electric discharge machining, the electrode material and cermet material are relatively moved, and electric discharge and short circuit are repeated between them, whereby the cermet material is formed. A method for strengthening the surface of a cermet material, which comprises coating the metal phase lacking portion on the surface of the cermet material with the metal phase forming the material of the electrode material. 2. The method for strengthening a surface of a cermet material according to claim 1, wherein the electrode material is made of the same metal phase as the metal phase in which the cermet material is missing. 3. The method for strengthening a surface of a cermet material according to claim 1, wherein the electrode material is made of a different kind of metal phase suitable for compensating for the missing metal phase in the cermet material. 4. The method for strengthening a surface of a cermet material according to claim 1, wherein the electrode material is a composite material of the same metal phase material as the missing metal phase of the cermet material and a different metal phase material.