Characterisation of super duplex stainless steel by optimisation of EBSD parameters

Abstract

Electron backscatter diffraction (EBSD) was used to characterise the microstructure of a super duplex stainless steel (SDSS) alloy Zeron 100 and the intermetallic phases sigma and chi in this material. The material was analysed in three conditions; as-received, heat-treated at 900 C for 8 min and heat-treated at 750 C for 4 h. Heat treatments were performed to introduce the intermetallic phases in the steel. It is difficult to get reliable indexing of the sigma and chi phases due to noisy and overlapping patterns. To get the best results, the Hough transformation parameters were optimised and an averaging technique was used. The optimisation was done by removing some of the reflectors in the sigma- and chi-phases in the original TSL material files used for pattern indexing. By changing Hough parameters, considerable improvements in the indexing of the patterns were observed along with the increase of average confidence index (CI) value for both intermetallic phases. The applied SEM, Zeiss Ultra 55 FESEM was equipped with a NORDIF UF-1100 EBSD detector to acquire and stream patterns to HD. Indexing and data processing were performed by TSL/OIM 7.3. In the present study, at the most four different phases are present in the SDSS.