If stress relieving austenitic stainless will consistently mitigate SCC please post a specific result. Tough with SCC one can never say never.
Essentially all our plan site is comprised of process vessels constructed of, 304, 304L, 316 S/S. We have tried at various time to stress relieve vessels or piping to prevent SCC , mainly of the Chloride variety. I can say that in all cases stress relief wasn’t worth the time and money spent for what little benefits achieved, most of the time were not measurable. We have chlorides coming both from the inside and outside. As most of you know insulation is one of the biggest culprits, even with low chloride insulation. In a hot 120̊C high HNO3/Organic area we have Nitrosyl Chloride that will attack and crack butter.
In some very specific cases if you had just evaluated the data you would have said that stress-relief made things worst. We saw far superior results with stress relief of C/S (for NH3, Amines) than we ever saw with S/S. As mention in previous posts the actual process of stress relieving S/S is fraught with problems and possibilities of thing going wrong. We had them all. We also tried to use Quench Annealing again not worth the effort as a post fabrication process.
As most of our problems steamed from chlorides our sister plant had problems with thio-chemicals. They also didn’t have the success with stress relieving as would have been expected.
On the head problem which side is the SCC occurring inside or outside? We have had heads QA after forming but not after welding. It was an add on to the cost even though it was that great of an effort.
The ferritic 400's, especially 430 S/S, have to be annealed if welded on.