Abstract
This paper describes the stress corrosion cracking (SCC) behaviour of the cold worked AISI Type 316L stainless steel (UNS S31603) in a concentrated lithium salt solution at elevated temperature. Using the slow strain rate technique, SCC experiments were carried out on 20% and 40% cold worked materials in a 10g LiOH / 100cc H2O solution at 95 °C under electrochemical potential-controlled conditions. The SEM observation of the fracture surfaces indicates that the SCC behaviour of the cold worked 316L steel is essentially different from that of the solution annealed steel. A ductile fracture of cold worked samples occurred under open circuit conditions (~-280 mV vs SCE) and also at -200 mV (vs SCE), but slight intergranular attack was found in the near surface region of cold worked specimens when the electrochemical potential of cold worked samples was controlled at -120 mV (vs SCE). Moreover, SCC was observed when the experiments were conducted at +100 mV (vs SCE), and the intergranular SCC of solution annealed material changes into a mixed SCC mode, or a dominant transgranular SCC with an increase of cold work to 20% and 40%. Compared with the SCC behaviour of the solution annealed 316L, the present results show that cold work significantly improves the resistance of 316L stainless steel to intergranular SCC in the hot lithium hydroxide environment, while the susceptibility to transgranular SCC of cold worked 316L stainless steels increases with increasing extent of cold working. These effects of cold working on the SCC behaviour of 316L stainless steel in the hot lithium hydroxide solution are discussed with respect to electrochemical and microstructural phenomena.
