Austenitic stainless steels have for some time been used as superheater tubes in the electricity generation industries in harsh environments with temperatures as high as 650°C at pressures of some 200 atm; they are expected to provide reliable service for 30 years or more. Their detailed mechanical properties are dependent on the stability of the microstructure, particularly the formation, dissolution, and coarsening of precipitates. Although the precipitation processes have been studied extensively, there remain important discrepancies. It is known that small changes in the chemical composition or thermomechanical processing can profoundly influence the evolution of the microstructure. This review focuses on precipitation in creep resistant austenitic stainless steels, in particular wrought heat resistant grades containing niobium and titanium additions. Conventional alloys such as 18–8 and 16–10 are included together with the new NF709 (20–25) and other recent variants. Precipitates forming in a...

Precipitation in creep resistant austenitic stainless steels

Dislocation and grain boundary interactions in metals

Strength and ductility of 316L austenitic stainless steel strengthened by nano-scale twin bundles

Dislocation pile-up and grain boundary interactions in 304 stainless steel

The mechanical and corrosion properties of gas metal arc additive manufacturing (GMA-AM) 316L could be optimized by modifying the volume fractions of sigma (σ) and delta-ferrite (δ) phases through heat treatment. Results show that the heat treatment at 1000 °C to 1200 °C for one hour will not obvious influence the morphology of grains in steel but largely influence the contents of σ and δ phases. The heat treatment at 1000 °C effectively increases the amount of σ phase in steel, causing both increase of UTS and YS but decrease of El and RA. The heat treatment at 1100 °C to 1200 °C completely eliminates σ phase, leading to the decrease of UTS and YS but increase of El and RA. The σ phase has better strengthening effect than δ phase, but which may degrade ductility and increase the possibility for cracks generation in steel. Meanwhile, limiting the number of both σ and δ phases through heat treatment can improve the corrosion resistance of steel. And σ phase appears more detrimental impact on degradation the corrosion resistance of steel than δ phase.

Patrick Marshall

Papers

Austenitic stainless steels : microstructure and mechanical properties