Fractographic Observations on the Stress Corrosion Cracking of Some Austenitic Stainless Steels in MgCl₂ Solutions at 154 C Available to Purchase

The stress corrosion cracking of Type 304 austenitic stainless steels and alloys containing additions of Cu, Co, Ni, and Si in MgCl₂ boiling at 154 C (310 F) has been examined fractographically by scanning electron microscopy. Type 304 steels and alloys containing Co and Cu exhibit mainly a coalescing pattern of cracking as a result of multiple crack nucleation and some flat crystallographic regions. Alloys containing Ni and Si exhibit mainly flat fractures with some coalescence. Since the type of fracture observed is not dependent upon the stacking fault energy it is suggested that the principle effect is chemical: Crack nucleation is rendered difficult by additions of Ni and Si and the rate of propagation is lowered. Stress corrosion fracture in autoclave conditions appears to be similar. Some intergranular stress corrosion cracking occurred in all the alloys examined.