Microstructure evolution in boronized inconel 718 superalloy

Abstract

This study was focused on the pack-boronizing of Inconel 718 alloy tunderstand the microstructure evolution at 950 and 1050°C. Cross-section of the specimens boronized at 950°C showed the formation of silicide top layer and boride layer beneath to it. The separate layer of silicide was not observed for the specimens boronized at 1050°C. Ni-, Cr- and Fe- borides were observed in the boride layer. Unlike 950 °C, borides of various shapes, like the square, pentagonal and hexagonal, were observed in boride layer at 1050°C. Boride layer showed very good adhesion to the substrate. Maximum hardness of the boride layer was about 1600-2000 HV, which was about 4-6 times the hardness of the core. On the basis of obtained results, mechanisms of the microstructure development in the boride layer were proposed.