Method of Preparing Metal Matrix Composite and Coating Layer and Bulk Prepared Thereby

Abstract

This invention provides a method of preparing a metal matrix composite, and a coating layer and bulk prepared by using the same and in particular, it provides a method of preparing a metal matrix composite, which comprises the steps of providing a substrate; preparing a mixed powder comprising i) a first metal powder comprising a metal, alloy or mixture particle thereof, ii) a second metal powder comprising an intermetallic compound forming metal particle which forms an intermetallic compound along with the metal or the alloy element of the alloy, and iii) a ceramic powder comprising a ceramic or mixture particle thereof; injecting the mixed powder prepared above into a spray nozzle for coating; coating the mixed powder on the surface of the substrate by accelerating the mixed powder in the state of non-fusion at a speed of 300 to 1,200 m / s by the flow of transportation gas flowing in the spray nozzle; and forming the intermetallic compound by the thermal treatment of the coated coating layer, and a coating layer and bulk prepared by using the same, whereby the coating layer and bulk material with high wear resistance and excellent resistance against fatigue crack on the surface without causing damages such as heat strain to the substrate during the preparation of the coating layer can be provided.

Description

TECHNICAL FIELD[0001]This invention relates to a method of preparing a metal matrix composite, and a metal matrix composite coating layer and metal matrix composite bulk prepared by using the same. More particularly, the invention relates to a method of preparing a coating layer with wear resistance and excellent resistance against fatigue crack by securing high hardness by the dispersion of intermetallic compounds and ceramic particles without causing damages such as heat strain to a substrate in the process of preparing the coating layer and a method of providing a bulk which is prepared by separating the coating layer from the substrate, and a coating layer and bulk prepared thereby.BACKGROUND ART[0002]Dispersion reinforcement methods are used to improve the strength, hardness, wear resistance of alloys or metals. The dispersion reinforcement methods form a structure of intermetallic compounds being dispersed within the matrix of alloys or metals and their representative examples...

AI Technical Summary

Benefits of technology

[0029]In accordance with the method of preparing metal matrix composite of the invention and the metal matrix composite coating layer and bulk prepared by using the same, the production of metal matrix composites where intermetallic compounds and ceramic powders are dispersed is possible at low temperatures in comparison with the prior art so that there is no likelihood of causing damages by thermal strain and thermal shock to the substrates, the growth of intermetallic compounds was suppressed so that mechanical characteristics such as high temperature strength are improved, and the accumulation of heat on the coating layers is prevented and crack generation between the substrates and coating layers or inside the coating layers is suppressed so that resistance against crack generation due to the fatigue of the coating layers can be improved.

[0030]In addition, the invention can be applied to prepare members with excellent mechanical strength and also, it can be used to dispersion reinforce the surface of the existing members. In particular, as it is carried out at low thermal treatment temperatures, there is a slight possibility of exercising bad influence on the properties of the members upon surface hardening.

[0031]Besides, as the invention enables the processing under the environments of the thermal treatment temperature of relatively low temperature, low injection pressure of mixed powders and low transportation gas temperature, it can be manufactured with low costs and it is easy to mass production.

Problems solved by technology

Accordingly, such dispersion reinforcements as precipitation hardening are inappropriate for heat resistant aluminum alloys.

However, thin aluminum oxide (Al2O3) is formed on the surface of the aluminum metal powder in air even at room temperatures and this surface aluminum oxide membrane interferes the reaction of aluminum and other metal elements and thus inhibits the formation of intermetallic compounds.

Accordingly, as the powder metallurgy requires thermal treatment at a high temperature above the melting point of the alloys to produce intermetallic compounds, it proposes high costs resulting from high temperature operation and safety securing problems of facilities.

Further, the powder metallurgy involves complex manufacturing process including the suitable control of sintering atmosphere in order to prevent the oxidation of aluminum at high temperature in the course of sintering and according to the powder metallurgy, the formation of intermetallic compounds with transition metals having high melting points such as Ti or Ni has been known to be very difficult.

Besides, in the powder metallurgy, as a desired shape is prepared by a mold, it costs a lot to prepare the mold and it also has size limitation.

This method generates the same problems as in the casting.

In particular, where aluminum-transition metal alloys are prepared by the thermal spraying, coarse secondary phases are formed within the aluminum matrix and they exhibit inferior alloy characteristics.

Hence, according to the prior arts relating to dispersion strengthened aluminum alloys, especially, aluminum-transition metal alloys, it was difficult to obtain aluminum alloys where fine intermetallic compounds are evenly dispersed and only thermal treatment above the molten temperature of the alloys could form intermetallic compounds.

As discussed by the example of aluminum, the prior dispersion reinforcement methods all require high temperature processing resulting in high costs and have difficulty in that they have to prevent high reactivity at high temperature in the course of thermal treatment and in case of the powder metallurgy, it has size limitation resulting from the preparation of molds and incurs high costs.

Therefore, as the ceramic particles to be coated onto the substrates are heated to high temperature around 1000° C., which is a fusion temperature of normal ceramic particles, and then provided to the substrates by contact, they cause damages by heat shock to the substrates during the coating process, induce residual stress in the process of cooling thereby decreasing adhesion and shorten the life of the parts.

Also, due to the particle spray of high temperature, there is an increased risk with the handling of spray machine and complicated operation line is inevitable.

In addition, the fused particles of high temperature might react with impurities on metal matrix or its surface and form another compounds, thereby adversely affecting the properties of the material.

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