The influence of dissolved hydrogen on primary water stress corrosion cracking (PWSCC) of mill annealed alloy 600 was studied at temperatures ranging from 320°C to 360°C and hydrogen contents ranging from 0 to 4 ppm using the slow strain rate technique (SSRT). The results suggest that the susceptibility of Alloy 600 to PWSCC reaches the
maximum around 3 ppm of hydrogen content with the apparent activation energy of PWSCC depends on the hydrogen content. Therefore, the hydrogen content at which the susceptibility reaches the maximum may change by the temperature below 330°C. In addition, the surface of the specimen fractured by PWSCC shows a complex fracture mode which is typically observed on a fracture surface due to hydrogen embrittlement,on which intergranular and ductile fractures are alternately observed along
a crack propagation line. Keywords alloy 600, MA600, SCC, PWSCC, dissolved hydrogen, activation energy, hydrogen embrittlement, complex fracture surface, intergranular fracture