Factors Inducing Intergranular Fracture in Nickel-free High Nitrogen Austenitic Stainless Steel Produced by Solution Nitriding

Fe–25mass%Cr–1.1mass%N alloys with different impurity content were produced by solution nitriding and then subjected to tensile tests at ambient temperature. Yield strength and tensile strength of the alloys are much higher than those of conventional austenitic stainless steels, but the brittle intergranular fracture is caused during uniform deformation without local elongation. It was confirmed that the intergranular fracture takes place at high angle random boundary and that the grain boundary segregation of impurities significantly promotes intergranular fracture. Deformation-induced martensite did not concern the intergranular fracture. In addition, it was suggested that marked stress concentration is caused at grain boundary by the piled-up dislocations in planar array and it would be one of the important factors inducing intergranular fracture.