Starting in 1893, German scientists used tungsten trioxide and carbon heated together in an electric furnace to a high temperature to make tungsten carbide, and tried to use their high melting point,High hardness and other characteristics to make drawing die, etc., in order to replace the diamond material.ButWC spraying powderhas not been used in industry because of its high brittleness, easy cracking and low toughness.

In the 1920s, German scientist Karl Schroter found that pure tungsten carbide could not adapt to the drastic stress changes formed in the drawing process. Only by adding low-melting metal into WC could the roughcast have certain toughness without reducing its hardness.

Schroter first proposed in 1923 the patented method of powder metallurgy, in which tungsten carbide is mixed with a small amount of ferrous metals (iron, nickel, cobalt), then pressed into shape and sintered in hydrogen at temperatures above 1300 to produce a hard alloy.

So far, the development oftungsten carbide sprayingpowdergenerally spans three stages. The first phase consists of powders and wires with metals and alloys as the main components, including aluminum, zinc, copper, nickel, diamond and iron metals and their alloys. These materials are made into powders, produced by primary grinding methods such as crushing and mixing, and manufactured by drawing wire or alloy wires of a certain diameter. These materials are mainly used in flame powder spraying, line spraying and arc spraying processes. Coating function is relatively simple, general corrosion resistance, wear resistance, small application surface; The second phase began in the mid-1950s. It has been found that it is necessary to improve the spraying process of tungsten carbide to obtain a more wear-resistant coating in order to solve the problem of mass wear in industrial equipment. After several years of efforts, the introduction of self-fusion alloy, the development of flame spray welding process. This is known as "hard surface technology". Self-fusion alloy is made by adding B, Si and Cr into the metal of Ni, Co and Fe groups, which can form eutectic alloying elements and antioxidant elements with low melting point. After tungsten carbide is sprayed, it is heated and remelted to obtain a hard coating. This technique was inspired in part by the welding surface treatment process.

Thanks to their high hardness, high metallurgical bonding and excellent oxidation resistance, these coatings have taken a big step forward in terms of wear resistance and oxidation resistance. The appearance of self-fusion alloy greatly promoted the development of tungsten carbide spraying technology. Another technological breakthrough at this stage is the emergence of plasma spraying equipment. Plasma flame up to 10,000 degrees, almost all materials can be sprayed. As a result, people began to think and develop a series of ceramic materials and metal ceramic materials. In fact, only after the mid-1970s, after the 8th international thermal spraying conference held in Miami in 1976, with the rapid development of the aviation industry, these materials really found a way to be applied, and high-performance, are gradually emerging. Technical wear-resistant, high temperature resistant, anti-gas corrosion and heat insulation surface engineering coating materials, so that thermal spraying technology from the simple maintenance workshop began to enter the aerospace and aircraft and other high-tech industries, and solve the headache of many metallurgical engineers. Not only did aircraft designers worry about the technology dropping planes from the sky, but since then, aircraft engines with more than 100 parts have been included in the specifications and must be sprayed with tungsten carbide to meet the designer's requirements. In the third stage, a series of composite powders and self-adhesive primary spraying powders appeared in the mid-1970s. It was not until the 1980s that sandwich lines were introduced to the market as arc sprayed materials.

Related link:

http://www.wococarbide.com/Transaction/en_information.html

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