Modeling of the microstructural evolution and lifetime prediction of MCrAlX coatings on Nickel based superalloys in high temperature oxidation

• At high temperature, MCrAlX coatings are deposited onto the surface of superalloy to provide oxidation and corrosion protection by forming a thermalgrowing oxide scale. In this project, the oxidation behavior of an HVOF CoNiCrAlYSi coating on IN792 was studied in both isothermal oxidation (900, 1000 and 1100 °C) and thermal cycling (1100-100 °C). The microstructural evolution in the MCrAlX coatings after oxidation was investigated. It was found that Al-rich β phase is gradually consumed due to two effects: surface oxidation and coating-substrate interdiffusion. Some voids and oxides along the coating-substrate interface, or inside the coating, were considered to play a role in blocking the diffusion of alloying elements. Based on the microstructural observation, an oxidation-diffusion model was developed by using Matlab and DICTRA software to predict the lifetime of MCrAlX coatings. Several effects influencing the microstructural evolution were included: surface oxidation, coating-substrate interdiffusion and diffusion blocking. The results showed good agreement between the experimental composition profiles and modeling ones. Furthermore, by choosing suitable diffusion blocking factors, the accuracy of coating life prediction could be improved.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

MCrAlX coating; HVOF; Life prediction; Interdiffusion; Oxidation; Diffusion blocking

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