Enhancing yield strength of high nitrogen austenitic stainless steel

Abstract

Increasing the yield strength of high nitrogen austenitic stainless steel is important both scientifically and commercially. In this work, 18Mn18Cr0.6 N steel was cold rolled and annealed at 800 °C. the microstructure was investigated using electron backscatter diffraction, transmission electron microscopy, and X-ray diffraction. The yield strength was examined through tensile tests. The fracture morphology was studied by scanning electron microscopy. The corrosion resistance was analyzed through potentiodynamic polarization tests. Unusual dispersed fine globular Cr2N precipitates, rather than usual detrimental discontinuous cellular Cr2N precipitates, were obtained in 18Mn18Cr0.6 N steel after thermomechanical processing that comprised 70% cold rolling and 20 min annealing at 800 °C. the yield strength was increased by ~228 MPa, up to 910 MPa, because of the precipitation-strengthening effect of Cr2N. The ductility remained well. Cr2N precipitation behavior was analyzed. The strengthening effects of Cr2N, grain size, and interstitial elements on yield strength and their inter-relationship are discussed. This study provides a new insight into enhancing the yield strength of high nitrogen austenitic stainless steels