Studies of stress corrosion in X12Cr13 and X20Cr13 steels used for rotor blades of steam turbines have been conducted for determining the average rate of corrosion cracking development da / dt. Specimens were exposed to the salt mist environment of 1,2 ppm NaCl concentration in temperature of 60° C. The research environment represents the initial condensate of humidity from 3÷4%. Average rate of corrosion cracking development for specimens of the X12Cr13 is by 0,005 µm/h higher from specimens of the X20Cr13 steel. Course of the corrosion cracking initiation depends to a high degree on metal structure, and probably the close value of cracking propagation rate depends on the similar structure of those steels – high-tempered martensite with carbides at grain boundaries.
The subject of the research was the installation of a water steam used in the chemical industry. Penetration tests revealed an extensive network of cracks on the surface of steel and welds. Metallographic studies, chemical composition analysis, EDX anal-ysis were performed. Thermal treatment of steel was carried out and microhardness measurements were made. The results of the tests showed that stress corrosion was the main reason for the occurrence of cracks.
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