Effects of N and Cu on the precipitation and the creep life of 316 L austenitic stainless steel at 650 °C

N and Cu were incorporated in 316L austenitic stainless steel in order to improve the creep life at 650 °C and 700 °C with a stress range of 100–250 MPa. An increased amount of N in solid solution strengthened the matrix and suppressed the coarsening of M23C6 precipitates, which improved the creep life. Low stresses allowed Cu-added alloys to rupture after the precipitation of the Cu-rich phase, which strengthens the matrix. Therefore, the addition of Cu enhanced the creep life only under low stresses while the positive effect of Cu was inconspicuous under high stresses.