Study on high-strength high-N austenitic stainless steel prepared by spark plasma sintering

Abstract

A novel method consists of nitriding and spark plasma sintering was used to fabricate high nitrogen austenitic stainless steel (HNASS). The influences of nitrogen contents in austenitic stainless steel on microstructure, mechanical properties and corrosion resistance were investigated. Results show that the ferrite-austenite phase transformed into single austenite phase after nitriding uptake. The nitrogen contents determined the type of precipitates chromium nitrides, and the contents higher than 2.77 wt. % promoted the formation of CrN, which corresponds well with thermodynamic results. The fine grain size (round 3μm) and precipitated chromium nitrides (200~600 nm) lead to a high yield strength of 817-1111MPa, which exceeds conventional stainless steel. The corrosion rate decreased with increasing content up to 1.29 wt. %, then the corrosion rate increased with increasing nitrogen contents, which results from the combined effect of solute nitrogen and nitrides.