OXIDE SCALE GROWTH ON MCRALY COATINGS AFTER PULSED ELECTRON-BEAM TREATMENT

A new electron beam treatment method was applied to the surface of LPP S-MCrAlY coatings to improve the oxide scale behavior. The electron be am generated by the newly developed facility GESA has a diameter of ab out 10 cm and sufficient power density to melt a surface layer of abou t 20 mu m of this area by just one electron beam pulse. Cooling rates are around 10(6) K/s and result in a nanometer grained single phase st ructure of the surface layer, that solidifies directionally. The high roughness of the as sprayed surface is reduced by the GESA process fro m R-A = 5 to 1.5 mu m. The oxidation behavior of treated coatings at 9 50 degrees C in air was examined. During oxidation a single phase alph a-alumina scale developed on the treated surface with a considerably l ower growth rate as compared to the untreated coatings. Therefore, it is expected that electron beam treatment improves the oxidation resist ance of MCrAlY coatings and their suitability as a bond coat for EBPVD thermal barrier coatings. (C) 1998 Published by Elsevier Science S.A. All rights reserved.