2025 Volume 74 Issue 1 Pages 2-8
In order to clarify the fissure formation mechanism, the initiation and growth behavior of fissures in Ni-added steel in an ammonium thiocyanate environment was investigated in-situ observation. The fissure was a transgranular crack, and the matrix in the crack tip was also dissolved. After the fissure occurred, crack propagation and crack stagnation were repeated. This is considered to be an APC type SCC. It is thought that the addition of Ni created a potential difference between the areas where NiS film was formed and the areas where it was not, causing local corrosion, and stress caused NiS film to repeatedly break and form, promoting fissure.
