Effects of temperature on the β-phase depletion in MCrAlYs: A modelling and experimental study towards designing new bond coat alloys

This paper investigates the effects of varied temperature conditions on the kinetics of β-phase depletion in MCrAlYs by DICTRA diffusion simulations and experimental observations. A commercially available MCrAlY composition and two modelled compositions were examined at temperature regimes of 1000 °C, 1100 °C and 1200 °C. A previously developed temperature-dependent oxidation model was used at the boundary to examine the β-phase depletion kinetics at different temperatures. The oxide growth kinetics and the corresponding Al flux were calculated based on the oxidation model. The MCrAlY phase equilibrium calculations were conducted in Thermo-Calc and the oxidation-diffusion simulations were carried out using the finite difference diffusion software, DICTRA. It was found that the MCrAlYs exhibit a predominantly dual-phase γ + β structure at 1000 °C and above. It was revealed that varying the temperature had a strong effect on the β-phase depletion in low Al-content MCrAlYs from DICTRA simulations and available experimental measurements. In addition, it was demonstrated from the diffusion simulations that MCrAlYs with high Al content exhibit an enhanced lifetime in maintaining the two-phase structure with less β-phase depletion at high temperatures due to the high Al and β-phase content.