Microstructural evolution of the heat affected zone of a Co-Ti-W alloy upon laser cladding with a CoNiCrAlY coating

Abstract

We report on the microstructural evolution of the heat affected zone of a γ/γ′-strengthened Co–Ti–W alloy upon laser cladding with a CoNiCrAlY coating. Using electron microscopy and atom probe tomography we observed two distinct heat affect zones, namely γ islands containing γ′ precipitate (∼ 45 nm in size) colonies and heat affected γ/γ′ regions outside the γ islands comprising fine γ′ precipitates (∼ 25 nm in size). Based on the experimental data and thermodynamic calculations, we propose a model for the formation of these two heat affected zones and discuss the differences in the observed precipitate sizes.