Overview no. 63 Non-equilibrium grain boundary segregation of boron in austenitic stainless steel—I. Large scale segregation behaviour

Abstract Secondary ion mass spectrometry (SIMS) has been used to study boron grain boundary segregation in austenitic stainless steels of the types 316L (containing 40ppm or less than 1 ppm boron) and “Mo-free 316L” (23 ppm boron). The influence of the cooling rate (0.25–530°C/s) was studied for three starting temperatures: 900, 1075 and 1250°C. Boron segregation was found after all heat treatments. The segregation behaviour was mainly of the non-equilibrium type. The same general segregation behaviour was found regardless of boron content and for both boron isotopes. Intergranular precipitation was predominant in the “Mo-free 316L” steel whereas mainly intragranular precipitates were found in the 316L steel. Boron was also often associated with aluminium- or sulphur-containing inclusions. A discussion of the results and of the ability of SIMS to detect boron grain boundary segregation is given.