A COMPARATIVE STUDY of the ISOTHERMAL OXIDATION BEHAVIOUR of APS, VPS and HVOF CoNiCrAlY COATINGS

MCrAlY coatings are applied as bond coat for thermal barrier coating manufacturing or alone to protect the base materials of hot sections of power generation plants and aircraft engines from high temperature oxidation and hot corrosion condition.
In function of the operating conditions of the component to be coated and/or of economical considerations, MCrAlYs can be applied by different thermal spray techniques. The oxidation behaviour and the oxidation resistance depends not only on the composition and on the thickness of the coating, but also on the coating manufacturing process which can influence microstructure, composition, porosity and surface morphology.In the present work, by means of Vacuum Plasma Spraying (VPS), Air Plasma Spraying (APS) and High Velocity Oxy-Fuel (HVOF) techniques, coatings of comparable thickness were deposited onto a superalloy substrate by using a CoNiCrAlY powder of the same composition. Samples were isothermally oxidized at 1000°C for different periods up to 3000 h. Before ad after the furnace tests samples were extensively characterized. The different properties and characteristics of the coatings were analysed and discussed.