Effects of Cold Work on Stress Corrosion Cracking of Type 316L Stainless Steel in Hot Lithium Hydroxide Solution

The stress corrosion cracking (SCC) behavior of cold-worked AISI type 316L (UNS S31603) stainless steel (SS) in a concentrated lithium salt solution at elevated temperature was investigated. Using the slow strain rate technique, SCC experiments were carried out on 20% and 40% cold-worked materials in a solution of 10g lithium hydroxide (LiOH) and 100 cm3 H2O at 95°C under conditions with controlled electrochemical potential. Observation of the fracture surfaces by scanning electron microscope indicated the SCC behavior of the cold-worked steel was essentially different from that of the solution-annealed steel. A ductile fracture of cold-worked samples occurred under open-circuit conditions (~ –280 mVSCE) and at 200 mVSCE. Slight intergranular attack was found in the region near the surface of cold-worked specimens when the electrochemical potential was controlled at –120 mVSCE. SCC was observed when the experiments were conducted at +100 mVSCE. Intergranular stress corrosion cracking (IGSCC) of solution-annealed material changed into a mixed SCC mode, or a dominant transgranular SCC (TGSCC) with an increase of cold work to 20% and 40%. Compared to the SCC behavior of the solution-annealed 316L, the results showed cold work improved significantly the resistance of 316L SS to IGSCC in the hot LiOH environment. Susceptibility to TGSCC of cold-worked 316L SS increased with increasing extent of cold working. These effects were reviewed with respect to electrochemical and microstructural phenomena.