鉄基超合金A286の破壊形態に及ぼす内部水素の影響

抄録

In order to experimentally verify the fracture mechanism of a precipitation-hardened superalloy with internal hydrogen, we performed SEM observation of fracture surface and cross sectional area beneath the fracture surface of an A286 iron-based superalloy subjected to an internal hydrogen tensile testing, which was carried out in air after being charged with hydrogen under 100-MPa hydrogen gas at 270 oC. The internal hydrogen drastically deteriorated the ductility of the precipitation-hardened A286, accompanied by formation of many facets on the fracture surface. The presence of hydrogen may make dislocations easier to pile up at grain boundaries, inducing nanovoids, followed by microcracking along the grain boundaries. Consequently, many tiny dimples occurred in numerous facets on the fracture surface. The observation results imply most of the facets were formed due to dislocation pile-ups at the grain boundaries which were enhanced by the presence of hydrogen and subsequent growth to the microcracks.