The Structure and Protective Properties of Complex Chromium, Ti-tanium, Aluminum Based Diffusion Coatings on U8A Steel
DOI:
https://doi.org/10.20535/1810-0546.2015.6.52749Keywords:
Steel У8А, Diffusion coating, Plating, Titanium aluminizing, Corrosion resistance, MicrohardnessAbstract
Background. Modern materials work under stringent conditions of simultaneous action of high production speeds, high temperatures, aggressive environments, and therefore the materials they are made of must have an integrated protective properties: to combine wear resistance, high crack resistance, chemical stability at elevated temperatures, high corrosion resistance. Despite the large number of known types of coatings and their methods of obtaining scientific aspects of creation of coatings with a wide range of protective properties is not sufficiently developed.
Objective. Study of phase and chemical compositions, structure and protective properties of coatings on U8A steel, obtained by combining of diffusion chromium plating with the subsequent titanium aluminizing.
Methods. The coating was applied on the surface of the U8A steel. On the first stage, the gas plating at a temperature of 1050 °C for 4 hours was carried out. On the second stage titanium aluminizing of powder coat at a temperature of 1050 °C for 4 hours was carried out. X-ray diffraction, electron-probe, metallographic, durometric studies were conducted using known methods of physical materials science. Corrosion tests by gasometrical method were carried out.
Results. It is shown that as a result of saturation on the steel surface a multilayer coating is formed consisting of carbides of chromium, titanium, intermetallic compounds of titanium, aluminum, chromium. It has been established that the microhardness of multilayer coatings based on chromium carbides, titanium carbides, intermetallic metals is 5.8–34.0 GPA. It is shown that the application of complex coatings based on chromium, titanium, aluminum increases the resistance of U8A steel in many aggressive environments.
Conclusions. Complex chromium, titanium, aluminum saturation of U8A steel allows obtaining coatings with a total width of 27.5–30.5 µm, which ensures high corrosion resistance in various industrially important aqueous corrosive solutions.
References
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