Effect of Nitride and Carbide Forming Elements on Stress Corrosion Cracking of Austenitic Stainless Steel in Boiling MgCl2 Solution

Effect of less than one per cent of aluminum, titanium, vanadium, zirconium, niobium or uranium and heat treatment on the stress corrosion cracking (SCC) of 18Cr-20Ni or 18Cr-16Ni steel was investigated in boiling magnesium chloride solution at 151°C. The results indicate that the above alloying elements have no appreciable influence on the SCC resistance of stable austenitic stainless steel if they do not form nitride or carbide. The addition of aluminum, titanium, zirconium, niobium or uranium improved the SCC resistance of the nitrogen contaminated steel, possibly by decreasing the nitrogen content in solid solution, while vanadium, a weak nitride former, showed no effect. If carbide is precipitated, the SCC life is lowered since the carbon content in solid solution is decreased. It was indicated that aluminum, which forms nitride but does not react with carbon in solid solution, and uranium could be useful alloying elements in improving the SCC resistance of the air-melted stable austenitic stainless steel which might be contaminated with nitrogen.