Microstructural stability and resistance to IGC and IGSCC of thermomechanically treated types 304 and 316 stainless steels

Thermomechanical treatment consisting of carbide stabilizing aging of cold worked materials followed by low temperature recrystallization heating (SAR process) made the standard stainless steels highly resistant to intergranular corrosion and cracking in otherwise susceptible environments. After various reheating thermal exposure several kinds of IGC and IGSCC susceptibility tests were made on the optimized SAR treated materials to see the critical conditions for the microstructural stability. The microstructural stability was maintained up to 8250C and 8750C in Types 304 SAR and 316 SAR respectively. SAR treated materials showed no IGC and IGSCC susceptibility under the SSRT in 2880C oxygenated pure water, under the constant load tests in boiling 20% MgCl2 solution and in the hot corrosion environment. In addition, the improved mechanical strength of SAR treated materials relative to the conventional materials is one of the advantages to maintain high strength in those environments. (author)