フラクトグラフィ 電子チャネリングパターン法による応力腐食割れ破面解析

Abstract

Stress corrosion cracking (SCC) of austenitic stainless steels in a boiling 42% MgCl2 solution at 416K was studied fractographically by scanning electron microscopy. The crystallographic orientations of transgranular SCC were determined with the aid of electron channeling patterns (ECPs) obtained from the fracture surfaces. By means of the two-surface trace analysis using the single crystals of SUS304, SUS316 and SUS310S steels, the respective crack orientations of {100} (partly {110}), {210} and {100} plane were found in relation to the crystallographic characteristics of cracking. The distinct ECPs were obtained after relief of internal strain by the heat treatment in a vacuum, though the ECPs obtained directly from the fracture surfaces were very indistinct. Thus the crack orientations determined by the ECPs coincide well with those by the above two-surface trace analysis. The technique with ECP is also applicable to the determination of crack orientation of polycrystalline, and is superior as a microscopic fractographic analysis of SCC.