On the role of Al/Nb in the SCC of AFA stainless steels in supercritical CO2

Abstract SCC of a series AFA stainless steels with different Al and Nb contents were studied in supercritical CO 2 by SSRT. The results show that element plays precipitation strengthening on the mechanical properties, while it shows few effects corrosion properties. surface oxide film Al-free material only consisted amorphous Cr O 3 Cr-rich spinel. With addition Al, layers are formed significantly decreases diffusion, thus inhibiting initiation SCC. Fe 4 fills interior cracks both Al-containing materials. layer is at crack tip Because matrix grains large, protective can be tip, which cannot completely hinder outward diffusion ions walls its effect propagation limited.