INFLUENCE OF THE MICROSTRUCTURE OF PLASMA-DEPOSITED MCRALY COATINGS ON THEIR TRIBOLOGICAL BEHAVIOR

MCrAlY coatings (CoNiCrAlY) were thermal sprayed under various atmosph eres (air, argon, vacuum) on a nickel-based superalloy (Hastelloy X). Their microstructures (porosity. presence of oxides and phase composit ion) and mechanical properties (hardness and Young modulus) were chara cterized. The friction behaviour of these coatings sliding against a l ow-pressure plasma sprayed NiCoCrAlYTa coating was evaluated under fre tting conditions. The study focused mainly on the different degradatio n mechanisms that may occur. Depending on the coating microstructure: two kinds of damage were observed: particle detachment and microstruct ural transformation (tribologically transformed structure). Adhesion a nd oxidation wear were also studied. (C) 1998 Elsevier Science S.A.