Orientation studies have been made on several different austenitic stainless steels, using photogrammetric and electron channeling techniques. The fracture facets produced by SCC in boiling aqueous MgCl2 (155 °C) were large and relatively flat in the case of type 310 steels, and the fracture plane was found to be at or near {100}. The transgranular stress-corrosion fractures in type 304 steels were more complex, and there was considerably more scatter in the orientation determinations. However, the orientations of the fracture facets in these steels were clearly not {100}, but fell into two distributions, one near {211} and the other near {110}. Electron diffraction studies from the fracture surfaces indicated the presence of α′ and martensites in the type 304 but not in the type 310 cases; the possibility that this was responsible for the differences in fracture planes is discussed. Studies were also made of a type 304 specimen which had failed by SCC at 289 °C. No martensitic phases were detected at the fracture surfaces in this case, and the fracture facets were large and flat, similar to those for type 310. Cleavage-like fracture surfaces were also produced in type 304 steels by hydrogen embrittlement, using both gaseous hydrogen and cathodic charging, but the facets were too small for precise orientation determination.

Studies of the orientations of fracture surfaces produced in austenitic stainless steels by stress-corrosion cracking and hydrogen embrittlement

Hydrogen-assisted quasi-cleavage fracture in a single crystalline type 316 austenitic stainless steel

Basic aspects of stress-corrosion cracking (SCC) in metallic materials are outlined, followed by a summary of the numerous mechanisms that have been proposed for SCC. The characteristics of transgranular and intergranular SCC in model systems, e.g. pure metal and single-phase alloy single crystals and bi-crystals under testing conditions that facilitate discrimination between mechanisms, are then described. The applicability of the various proposed mechanisms, such as those based on dissolution, hydrogen embrittlement, film-induced cleavage, and adsorption, are discussed in detail for these systems. Mechanisms of SCC in complex commercial alloys are then considered in the light of these studies on model systems.

Mechanistic and fractographic aspects of stress corrosion cracking

The crystallography of stress corrosion cracking in face centered cubic single crystals

A review of the crystallography of stress corrosion cracking

Crystallography, morphology, and kinetics of stress corrosion cracking (SCC) in austenitic stainless steels exposed to boiling, aqueous 45% magnesium chloride solution were studied on single crystal specimens of a Type 316 stainless steel. Notched specimens of selected orientations were stressed in bending, using a self relieving loading system. The variations of load during crack propagation were recorded and analyzed to obtain a relation between the crack propagation rate and other parameters. A single surface analysis of crack traces on the specimen sides and a two surface trace analysis on sections through flat regions of fracture surfaces were used in the determination of the crystallographic orientation of the cracking plane. Fracture surface topography and corrosion attack on slip steps were examined in a scanning electron microscope. The results of the crystal lographic analysis show that the stress corrosion cracks propagated on (210) oriented crystal planes. After an initial period, the...

R. F. Hochman

Papers

Crystallography and Kinetics of Stress Corrosion Cracking in Type 316 Stainless Steel Single Crystals