Stress-corrosion cracking of martensitic and ferritic stainless steels

Abstract

One of the limitations of stainless steels (a limitation which is sometimes overstated) is their susceptibility to stress- corrosion cracking (SCC). This has proved to be the greatest hazard with the face-centred cubicstructured austenitic grades, a review concerning which has already appeared in Int. Met. Rev. While the other three groups, martensitic, ferritic, and duplex (ferritic–austenitic) differ markedly in behaviour, there is susceptibility to SCC the degree of which depends on steel composition, heat treatment, and environment. This review is concerned with these last three groups. Consideration of the martensitic (hardenable) types is by subgroup; the simple carbon 12–13% chromium types, the alloyed temper-resistant variants, the precipitationhardening grades, and the controlledtransformation types. Influences of test technique, test environment, stee 1 composition, and steel heat treatment are noted and data discussed in terms of practical implications and cracking mechanism. Cracking is more likely with steel in the stronger states. It is considered that a form of hydrogen embrittlement plays a dominant but not necessarily exclusive role in SCC failures. Steel heat treatment and composition play an important part in establishing susceptibility, the latter sometimes in ways which are difficult to explain. Data for the stable ferritic and duplex steels are less extensive and there is a need for substantial further experimentation. A mechanism involving localized corrosion along a narrow front can be reasonably supported, but strong cases have been made for at least involvement of hydrogen. There is ample evidence that these steels can be used under circumstances where the austenitic types would fail.