Microscopic visualization of hydrogen diffusion in UNS S32750 super duplex stainless steel: Roles of crystal structure and grain size
Hiroshi Kakinuma, Saya Ajito, Motomichi Koyama, Eiji Akiyama
Abstract
The microscopic hydrogen diffusion in UNS S32750 super duplex stainless steel was analyzed using a polyaniline-nickel-based hydrogen video imaging system. The hydrogen flux in the body-centered-cubic ferrite (α) phases was larger than in the face-centered-cubic austenite (γ) phases, causing hydrogen diffusion from the α to γ phases. The order of the hydrogen flux was as follows: (high) the center of the α phases > near the α-γ boundaries in the α phases > near the α-γ boundaries in the γ phases > the center of the γ phases (low). The grain size of the phases also affected the hydrogen flux distribution. A small grain size of the γ phase led to a large hydrogen flux around the center of the γ phase, because the effect of the hydrogen outflux from the α phase to γ phase increased with decreasing distance from the α-γ boundary.