Partially correct.

Emad Kamil, I am not sure.

ISO 15156 requires the hardness reduction in materials to avoid stress cracking corrosion. However, there is an idea since the combination of stress and corrosion can causse this type of corrosion, increasing the strength of the material can be helpful to mitigate this corrosion.

I think hardness reduction can reduce the stress cracking corrosion risk and not increasing the strength of material.

Not always thee case. With cold worked and drawn 316L stainless steel, we have found that the strength goes up but SCC becomes more prevalent especially in a chloride environment. The answer depends on the material, environment, and the external stresses.

In general the statement is not true. However, it is considered as a function of the characteristic response of a material to stress concentration and electrochemical activities.

Mostly its not true because SCC is connected to presence of residual stresses and corrosive environment. However, if the strengthen process of material leaved stresses inside it will enhance the probability of SCC. So I cant see the positive relation between strength and SCC mitigation

Tarig. Very good answer. I agree with you. If we think about piping, system the possibility of stress cracking corrosion is in the areas where there is a residual stress such as welding and cold work like bending. The best strategy to avoid stress cracking corrosion is to reduce the hardness or changing the material.

Karan, yes but the easy approach of preventing SCC at weld area can be achieved by the proper design and fabrication of welding by means to mitigate the residual stresses produced from the welding process it self. materials with less C% content can help as well. (Ferritic and duplex stainless steels are less sensitive to SCC)

Tarig. Yes. You are right. It is very common to apply Post Weld Heat Treatment on Piping based on ASME B31.3 "Process Piping Code" on some materials like carbn steel with thickness less than 20mm or 19mm to reduce the residual stress.

Also reduction of Carbon Equivalent in carbon steel material through reduction of Carbon mainly but also other compounds like Mn, etc. Incraese the weldability of material.

Duplex Stainless Steel is more sensitive than austenic stainless steels such as SS316 to SSC (Sulphide Stress Cracking Corrosion), But of course less sensitive to SCC compared to austenitic stainless steels.

The other point is that SCC could come from chloride, amine, caustic, etc. The source of chloride which causes SCC can be due to fluid or due to marine atmosphere. The reason why we try to avoid SS316 in offshore industry is sensivity of this material against chloride. In some cases the material could be upgraded to 22Cr duplex or 6MO with higher resistance against chloride.

I see some confusion between residual stresses, hardness and base metal yield strength in the previous comments, sorry. First, I don't believe SCC will ever decrease with increase base metal yield strength, because the driving force (residual stress) is always proportional with the yield strength. Hardness (an indirect measure of the TENSILE strength) is sometimes indicative of this behavior, but should not be confused with the cause - driving force, but rather with an effect.

Similarly, carbon equivalent is only a partly indicator of HAZ hardenability, so it should not be brought into the initial question (yield strength increase is not always a direct consequence of hardenability - see microalloyed steels, or TMCP steels).

I hope that I was able to enforce the position that SCC will always increase with the base metal yield strength, for all other conditions being equal!