Abstract
SCC of Inconel 600 (In 600) and Incoloy 800 (Iy 800) in 50% NaOH at 140°C was investigated using a constant strain rate method under electrochemically controlled potentials. SCC took place at a primary active region (-0.90V, SCE) and a secondary passive region (-0.40-0.05V, SCE) in polarization curves at ε=4×10-3min-1. The former region; SCC was found in solution annealed In 600 and in both alloys for sensitized materials. In this region sensitized materials showed higher susceptibility to SCC and all materials showed intergranular cracking. The latter region; SCC was found in both alloys and there was not so much difference in the susceptibility between annealed and sensitized materials. Transgranular cracking occurred around 0V and intergranular cracking became predominant at higher or lower potentials than 0V. Changing strain rate from 6×10-5 to 10-2min-1 for annealed materials at 0V, maximum susceptibility to SCC was obtained at ε=10-4min-1 for both alloys, and crack mode was intergranular at the strain rate. Further, mechanism of the SCC and relationship between these results and early works were discussed.
