Correct selection of coating materials is the key to ensuring coating performance. When selecting the coating material, the working conditions of the workpiece and the performance of the coating should be considered first, as well as the material, batch, economy of the workpiece and the proposed thermal spraying method. According to the function of the coating, the coating can be divided into corrosion-resistant coating, wear-resistant coating, wear-resistant sealing coating, high temperature thermal barrier coating, insulating or conductive coating, dimensional repair coating.
The failure of surface-coated workpieces during use is usually not caused by a single factor, so there is not necessarily a simple relationship between the satisfaction of the working conditions and the performance of the coating. The working conditions should be analyzed in detail, and one or more coating materials should be determined comprehensively considering the coating structure, physical, chemical, mechanical and other properties according to the references or experimental data.
Wear-resistant coating is one of the main application areas of surface coating technology. Although there is a rough relationship between coating hardness and wear resistance, hardness does not fully represent the wear resistance of surface coatings. Because different wear types have different requirements for material properties, wear is often accompanied by impact, corrosion, fatigue and temperature.
The selection of surface coating materials cannot blindly pursue high-performance or high-priced coating materials, resulting in unnecessary waste. High-priced and low-priced materials cannot even be used as the standard for selecting coating materials. On the premise, it is particularly important to use cheap coating materials as much as possible in mass production. For example, nickel-based alloys can be coated instead of cobalt-based alloys.
When choosing a surface coating material, the following steps can generally be followed:
(1) Analyze working conditions and parts performance to understand failure causes and requirements for coating performance;
(2) List available coating materials;
(3) Analyze the compatibility of the selected material with the base material and the applicable thermal spraying method;
(4) Carry out laboratory or field tests when necessary;
(5) The coating material is determined comprehensively considering the service life, cost and factory conditions;
(6) Determine the surface coating method and formulate the coating process.
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