Cyclic oxidation behaviour of different treated CoNiCrAlY coatings

► It has been investigated the oxidation behaviour of differently pretreated CoNiCrAlY coatings. ► The characteristics of the grown oxide scale influence directly the cooling rate. ► The lowest oxidation rate was exhibited by the EB and vacuum pretreated samples. High velocity oxygen fuel (HVOF) spraying method was used in order to obtain very dense and good adhesive CoNiCrAlY-coatings deposited onto nickel-based alloy. The coatings were differently treated (preoxidized, vacuum treated or electron beam irradiated) before their exposure to cyclic oxidation tests in air at 1000°C for periods up to 5h. Changes of the coatings morphology and structure were analysed by scanning electron microscopy (SEM) and X-ray diffraction technique (XRD). The surface temperature of the samples was measured during cooling, between the oxidation cycles, and finally was associated with the thickness of the grown protective oxide scale on the CoNiCrAlY-surface. The experimental results demonstrated that depending on the thickness respectively on the different structures of the grown oxide scale, the cooling rate of the sample surface will be different as well.