Abstract
Nitrogen addition is known to be one of the most effective ways of strengthening austenitic stainless steels while maintaining good properties of the steels. This study investigates Nb addition as an additional strategy to strengthen a high nitrogen austenitic stainless steel. It was found that Nb-containing steels developed Z-phase precipitates during homogenization and hot-rolling. Their fraction and size hardly changed by subsequent aging at 1050 °C. They effectively delayed grain coarsening and fine grains were maintained throughout the aging. The yield strengths of Nb-containing steels were always higher than those of Nb-free steel by 30–83 MPa. Quantitative analyses revealed that the major strengthening mechanism was grain boundary strengthening. The contribution from precipitation hardening was small because the precipitates were not sufficiently fine and the negative contribution from solid solution strengthening due to N consumption by the precipitation was also insignificant.
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