Banded structure and its distribution in friction stir processing of 316L austenitic stainless steel

• Published in: Journal of nuclear materials Vol. 420; no. 1; pp. 497 - 500
• Main Authors: Chen, Y.C., Fujii, H., Tsumura, T., Kitagawa, Y., Nakata, K., Ikeuchi, K., Matsubayashi, K., Michishita, Y., Fujiya, Y., Katoh, J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 2012; Elsevier
• Subjects: Applied sciences; Austenitic stainless steels; Banded structure; Chromium; Controled nuclear fusion plants; Depletion; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Friction stir processing; Fuels; Heat resistant steels; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; Precipitation; Sigma phase precipitation; Welding parameters; Corrosion resistance; Austenitic stainless steel; Band structure; Depletion; Cooling; Welding; Stainless steel; Nuclear reactor
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2011.10.053

► Friction stir processing (FSP) as a repair method. ► Sigma phase formed in the FSP zone. ► Low heat input contributes to restrain sigma phase precipitation.
Banded structures, which vary with welding parameters, were observed in friction stir processing of 316L austenite stainless steel. Sigma phase precipitation was detected in banded structures by transmission electron microscopy. The amount of banded structure had direct ratio relations with heat input. The higher the heat input, the larger the area of banded structures. This is attributable to slower cooling rate at high heat input, which results in longer exposure to the temperature range for precipitation. The formation of sigma phase produced Cr depletion, which resulted in largely degraded corrosion resistance. The present study suggests that low heat input (i.e. low rotation speeds, low working loads and high welding speed) contributes to restrain sigma phase precipitation.