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

Abstract

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 Alcontent MCrAlYs from DICTRA simulations and available experimental measurements. In *Manuscript Click here to view linked References 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.

Growth stress and interdiffusion analysis of NiCoCrAlYTa coating during oxidation

“…In the initial stage of oxidation, the stress value of prediction was higher than that of the experimentally determined. Since the oxides scale formed under oxidation condition was mainly consisted of α-Al 2 O 3 , which was considered as the most effective protective oxide for the low diffusivity of oxygen and metal ions in its hexagonal close-packed (HCP) structure [47]. In this case, the growth rate of the oxides scale was very low, contributed the difference with the prediction, indicating Equation (10) was not suitable for the short-time oxidation condition.…”

High-temperature oxidation resistance of NiCrAlY columnar microcrystalline coating deposited by EDS

“…It can form a stable protective alumina layer, and its unique composition design can meet specific performance requirements [1][2][3]. The NiCrAlY coating can promote the formation of Al 2 O 3 oxide film with slow growth, uniformity and strong adhesion at service temperature, which acts as a diffusion barrier layer at service temperature [4]. A large number of studies have shown that the oxidation resistance of Ni-rich MCrAlY alloy is better than that of Co-rich MCrAlY alloy under high-temperature oxidation environment.…”