High temperature oxidation behavior of laser cladding MCrAlY coatings on austenitic stainless steel

Abstract

The development of coatings has become technologically significant in many industries. A common approach in high temperature applications is the production of new thermal barrier coatings (TBCs). Laser cladding (LC) can be an alternative method to thermal spraying in the production of high quality bond coats in TBCs. In this work, dense coatings that formed adequate metallurgical bondswith the substrate were obtained by overlapping coaxial laser cladding. The oxidation behavior of the coating specimens was assessed by air furnace oxidation tests at 1100 °C for up to 200 h. The coatings' microstructures are composed of a γ matrix phase and a β interdendritic phase, confirmed by X-ray diffraction (XRD). At high temperatures, the growth and formation of oxide layers protect the underlying coating and substrate from oxidation at elevated temperatures. The possible formation and morphology of oxides on the oxidized surface were evaluated using scanning electron microscopy (SEM), XRD and atom force microscopy (AFM). The evaluation of the thickness and phases present in thermally grown oxide scales was evaluated using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy microanalysis (EDS), with a previous cut using the Focused Ion Beam Ga Column (FIB) method.