JPH0377153B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a method for producing a composite body in which a high-grade ceramic layer is adhered to the surface of a metal object using low energy.

(b) Background of the technology Composite materials that combine metals with ceramics such as nitrides, carbides, borides, and silicides have the advantage of the good workability and toughness of metals and the heat resistance and corrosion resistance of ceramics. It has high utility value as a material that has both wear resistance and wear resistance. In addition, in the manufacture of complex-shaped parts that are difficult to manufacture using ceramics alone, it is possible to reduce costs by using ceramics only in those parts where the functionality of ceramics is required.

Conventionally, there are so-called ceramic coating methods and thermal spraying methods as methods for producing composites of metal and ceramics for such purposes. However, these methods have the disadvantage that it is difficult to form a thick layer and that they are expensive.

Another possibility is to prepare a sintered ceramic body in advance and bond it to a metal to form a composite, but this method has not been put into practical use due to the difficulty of bonding metal and ceramics.

(C) Disclosure of the Invention An object of the present invention is to provide a method for manufacturing a composite of metal and ceramics at low cost and with almost no restrictions on shape. More specifically, a molded layer of mixed powder that can generate ceramics through an exothermic reaction between the mixed powders, or a mixed powder that can generate ceramics through an exothermic reaction between the mixed powders and the atmosphere, is formed on the metal surface. A part of the mixed powder compact layer is forcibly heated under pressure to start a reaction, and the reaction heat causes the mixed powder compact layer to react in a chain reaction to form a ceramic layer, while at the same time forming a metal surface. The present invention provides a method for producing a composite of metal and ceramics by bringing them into close contact with each other.

Ceramic sintered bodies are generally manufactured by a method of sintering or reaction sintering by externally applying a large amount of thermal energy to a molded body of ceramic powder or a molded body of a mixture that produces ceramics by reaction.

However, in many cases, the production of ceramics is an exothermic reaction, and the present invention has focused on this, and as a result of various studies, has been completed as a method for producing a composite of metal and ceramics.

Ceramics to which the present invention can be applied include a Carbide: TiC, ZrC, HfC, VC, NbC, Ta ₂
C, TaC b Nitride: AlN, TiN, ZrN, HfN, VN,
NbN, TaN c boride: TiB ₂ , TaB ₂ , ZrB ₂ , HfB ₂ d silicide: TiSi ₃ , ZrSi, MoSi _2, etc., and a mixed ceramic of two or more selected from these may also be used.

As the mixed powder forming the molded body layer, if the ceramic to be produced is a carbide, a mixture of a metal element and carbon is used, and if the ceramic to be produced is a silicide, a combination of a metal element and silicon is effective. When the ceramic to be produced is a boride, a combination of a metal element and boron can be used. On the other hand, when the ceramic to be produced is a nitride, it can be obtained by reacting a molded body of a metal element in a nitrogen gas or ammonia atmosphere.

In order to cause the above-mentioned mixed powder compact layer to react and form the desired ceramic, it is sufficient to heat a portion of the compact to a temperature sufficient to initiate the reaction, and heating methods such as heating with a heater are available. used. In order to cause a chain reaction in the entire layer of the mixed powder compact to form a complete ceramic layer, it is also effective to heat it from the outside as necessary. In this case as well, a chain reaction can occur with less heating energy than in the case of general sintering.

On the other hand, from the viewpoint of the purpose of the present invention, it is important to firmly adhere the ceramic produced by the reaction to the metal layer.

The present inventors have discovered that if a mixed powder compact layer for producing ceramics and a metal are caused to react under pressure, a composite layer with a ceramic layer in close contact with the metal surface can be created. I discovered that it is possible to form a body. There are two possible mechanisms by which a ceramic layer is formed in close contact with a metal surface. One is that a part of the metal surface that is in contact with the ceramic-generating mixed powder layer is melted by the reaction heat during ceramic generation, and the mixed powder is formed using capillary force and the pressure that is applied between the mixed powder compact and the metal. This is a case in which the mixed powder molded body reacts and becomes a ceramic at the same time as it penetrates into the pores of the body, and is brought into close contact with the body.

This mechanism occurs when there is little reaction between the metal and the ceramic product mixture and when the melting point of the metal is relatively low.

Another mechanism is when there is a significant chemical reaction between the metal and the ceramic-forming mixture, forming a multi-ceramic layer at the interface between the metal and the ceramic formed.

This will be explained below using examples.

Example 1 A mixed powder obtained by mixing titanium powder and carbon powder at a molar ratio of 1:1 was press-molded at a pressure of 2000 Kg/cm ² to form a green compact. This green compact was placed in a hot press mold with an iron block in contact and an electric heater in contact with the top surface of the green compact. In an atmosphere of Ar, heating from the outside of the hot press mold keeps the entire temperature at 1100°C and the hot press pressure is kept at 200 kg/cm ² , and the electric heater attached to the top of the compact is energized to heat the surface of the compact. The powder was heated to initiate a titanium carbide production reaction on the surface of the green compact. After the reaction had sufficiently started, the power supply to the electric heater was stopped, and then the hot press pressure and temperature were maintained for 20 minutes, then the temperature and pressure were lowered, and the sample was taken out. As a result of X-ray diffraction, it was found that the powder compact layer was almost completely made of titanium carbide. In addition, the hardness of the titanium carbide layer is Hv = 3000 Kg/mm ² and the shear strength at the interface with the metal is 30 Kg/mm ² , indicating that a composite is formed in which iron and titanium carbide are tightly adhered. Ta.

Example 2 A compact of titanium powder and an iron block were brought into close contact with each other to form a composite in the same manner as in Example 1.

Molding pressure of titanium powder is 1000Kg/cm ² , hot press temperature 1200℃, hot press pressure 200Kg/cm ² ,
The hot press atmosphere was nitrogen gas, and the reaction time was
The duration was 20 minutes.

The green compact layer was made of titanium nitride, and the hardness of the titanium nitride layer was Hv=2000 Kg/mm ² , and the shear strength at the interface with the metal was 35 Kg/mm ² .

Claims (1)

[Claims] 1. A mixture of at least one metal element selected from elements of group a, group a, and group a of the periodic table and at least one nonmetal element selected from B, C, N, and Si on the surface of a metal object. forming a powder compact layer;
A part of the mixed powder compact layer is forcibly heated under pressure to start a reaction, and the reaction heat causes the mixed powder compact layer to react in a chain reaction to form a ceramic layer and at the same time adhere to the surface of the metal object. A method for producing a metal-ceramics composite characterized by: