Oxidation behaviour of borided Incoloy 909

The oxidation behaviour of Incoloy 909 superalloy subjected to diffusion boronizing treatments was studied at 750 and 850°C in atmospheres of dry air and a mixture of dry air + water vapour for times up to 10 h. The oxidation behaviour of the coated samples was described by the parabolic rate law with activation energies of 26 and 21 kJ mol⁻¹ when oxidation was conducted in dry air or in the mixture dry air + water vapour respectively. Oxidation kinetics of the boronized coatings were sensitive to temperature and the oxidation environment promoting the development of a thick SiO₂ layer on top of the coatings which also included minor additions of other oxides that acted as a barrier that reduced oxidation. However, in the conditions that included water vapour boron-rich oxides were also formed and a different oxidation behaviour was experienced.