Microstructure and microtexture changes during solution nitriding to produce austenitic case on ferritic–austenitic duplex stainless steel

Abstract

The present paper reports an investigation into the microstructural changes occurring in a ferritic–austenitic duplex stainless steel during solution nitriding. Both microstructure and microtexture modifications as a result of nitrogenation have been studied, in addition to the interaction between solution nitriding, grain growth, and texture. Three microstructural zones were identified: a duplex ferrite–austenite region overlayed by a transition zone overlayed again at the surface by an austenitic zone. The solution nitriding led to nitrogen enrichment at the specimen surface, which in turn enlarged the austenitic field in this region. The ferrite dissolution here triggered secondary recrystallisation, accompanied by a texture change. Hence, the texture of the austenite in this region was different from that in the duplex region.