Pitting and Stress Cracking of 12Cr-Ni-Mo Martensitic Stainless Steels in Chloride and Sulfide Environments Available to Purchase

Laboratory melted 12Cr-Ni-Mo steels were tested in chloride/sulfide solutions at 60 C and at room temperature to evaluate their resistance to pitting and stress cracking in connection with environmental and metallurgical factors. H₂S had significant adverse effects on the pitting resistance of the martensitic stainless steels tested. Stress cracking at 60 C was associated in many cases with the formation of pits in chloride/sulfide solutions. Potentiostatic stress cracking tests revealed that in a sulfide solution at room temperature, cracking occurs by hydrogen embrittlement and in chloride/sulfide solutions, by active path corrosion. These steels were tempered at 600 C for the single temper treatment and 700 C followed by 600 C for double tempering. The double temper treatment intensified pitting and stress cracking at 60 C while improving stress cracking resistance at room temperature, as reported elsewhere. Fracture was mixed mode in the single temper condition and transgranular quasi-cleavage with double tempering regardless of solution temperature. The metallurgical changes associated with the temper treatments were studied and discussed.