Comparative Analysis of Diffusion Metallization Coatings Applied on Steel Parts

In this paper the positive and negative aspects of diffusion metallization of steels were reviewed. It was shown that at high heating temperatures and prolonged exposure under these temperatures, steels show a tendency to enlarge austenitic grain. Overheating can occur at high exposure temperatures (T>1000ᵒC), which can be rectified by repeated heating however if burning of the steel microstructure occurs, it cannot be corrected. Given these circumstances, when assigning diffusion metallization modes, it is necessary to consider the factor of overheating or burning of steel in the process of exposure to high temperatures. To avoid this phenomenon, it is recommended to use alternative low-temperature processes of diffusion saturation of steels. Nitriding, nitro-cementation, gas-thermal spraying of the surface of steels are shown as such examples. It was suggested that these processes in comparison with diffusion metallization are more promising and acceptable for the restoration of worn surfaces of steels in the manufacture of parts of specialized equipment. Given that the parts of specialized equipment work in extreme conditions, repeated high-temperature heating of these steels is not recommended.To overcome the shortcomings of the diffusion metallization, the most frequently used coatings are applied by CVD, thermal spray, and cloth cladding techniques. As an alternative promising solution, the development of innovative methods of diffusion saturation, like an ion plantation of atoms on a relatively cold surface of the part could also be considered. It is shown that diffusion metallization is most acceptable for saturation of the surface of non-ferrous metals and alloys with the hardest and wear-resistant compounds.