Correlation of chemistry, microstructure and ductile fracture behaviours of niobium-stabilized austenitic stainless steel at elevated temperature

The microstructural difference, which resulted from a variation in the chemistry, was systematically correlated with the ductile fracture properties of niobium-stabilized stainless steel (AISI type 347) at 316 °C. It was observed that the type, density and size of the precipitates varied with the carbon, nitrogen and niobium contents. J-R fracture resistance at 316 °C decreased as the density of precipitate increased. It was concluded that the coarse Nb(C, N) precipitates accelerated ductile crack propagation in the type 347.