Initiation behavior of stress corrosion cracking for type 316L stainless steel with controlled distribution of surface work hardened layer in high temperature water

The stress corrosion cracking susceptibility is strongly affected by the properties of surface work hardened layer. Therefore, to fabricate the samples with reproducible surface is required for quantitative SCC initiation tests. The main focus of this study is to establish the preparation method of SCC initiation test sample using face milling. Furthermore, CBB test was conducted to evaluate the SCC susceptibility of these samples. Face milling was conducted on the commercial type 316L stainless steels with the cutting parameters of feed and spindle speed. Micro Vickers hardness tests and stress measurements using XRD were carried out to evaluate the distribution of properties of SCC test samples. The results obtained are as follows; (1) The cutting mark spacing and the depth of cut were controlled by feedrate. (2) The spacing and local hardness of high and low plastic strained region, average and standard deviation of hardness on surface were controlled by depth of polishing. (3) Residual stress introduced by face milling was bi-axial tensile stress. (4) The hardness distribution in high plastic strained region is equivalent to damaged core shroud H4 and surface grinding. (5) SCC was initiated on high plastic strained region. (6) CBB test results suggest that SCC susceptibility is related to hardness and stress distribution. (author)