Improving creep strength of 316L stainless steel by alloying with nitrogen

The influence of nitrogen on the creep behaviour of 316L(N) SS has been studied at nitrogen levels of 0.07, 0.11, 0.14 and 0.22 wt.%. Creep tests were carried out at 923 K at stress levels of 140, 175, 200 and 225 MPa with rupture life up to 16,000 h. Creep rupture strength was found to increase substantially with increase in nitrogen content; rupture life increased almost 10 times by increasing nitrogen content from 0.07 wt.% to 0.22 wt.%. Steady state creep rate decreased significantly with increasing nitrogen content. The extent of internal creep damage and surface creep damage decreased remarkably with increasing nitrogen content, resulting in increased creep rupture strength. Solid solution strengthening, increase in Youngʹs modulus, decrease in stacking fault energy and matrix precipitation of carbonitrides have contributed to the increase in creep strength with increasing nitrogen content.