High temperature oxidation of HFPD thermal-sprayed MCrAlY coatings

NiCrAlY and CoNiCrAlY powders were thermal-sprayed using the high frequency pulse detonation method (HFPD) onto AISI 310 austenitic stainless steel sa mples in order to obtain dense, adherent high temperature oxidation resista nt coatings. The cyclic oxidation behaviour in air of both types of coating s was determined at a maximum temperature of 1273 K. The porosity, internal oxidation (after the first 8-h oxidation cycle), hardness, coating thickne ss and substrate-coating adherence were not significantly modified by the h igh temperature oxidation cycles. The surface phase composition was evaluat ed throughout the tests using X-ray diffraction and scanning electron micro scope techniques revealing the formation of a continuous and highly protect ive alumina layer. The oxidation kinetics of both coatings can be character ized by parabolic rate constants, which are very similar to those of pure a lumina. (C) 2001 Elsevier Science B.V. All rights reserved.