ＳＵＳ ３１０Ｓステンレス鋼に処理したアルミニウム拡散被覆層の破壊挙動

Abstract

Cracks occurred on the Al-diffused surface of specimens of type SUS 310S stainless steel during tension loading was observed by a plastic replica technique. The initiation of cracks depended on the Al concentration in the diffusion layer; the strain at which cracks initiated decreased and the number of cracks increased with increasing Al concentration. Cracks occurring at low strain grew with increasing crack opening displacement and a small increase in the number of cracks during tension loading. The fracture strength of the diffusion layer at strain in which cracks just initiated was estimated by the rule of mixtures, considered that the diffused material consisted of two layers of the diffusion layer and the substrate. The fracture strength increased with the increasing degree of order of the α2 phase in the diffusion layer. Energy accumulated in the diffusion layer during tension loading was calculated from a strain-stress curve as energy was released by crack formation. Energy decreased with the increasing degree of order of the diffusion layer. This phenomenon corresponded to the fracture behavior of the layer, that is, change in fracture surfaces from cleavage to intergranular fracture.