Oxide scale growth on MCrAlY bond coatings after pulsed electron beam treatment and deposition of EBPVD-TBC

Thin layers restructured by surface melting to approximately 30-mum depth on MCrAlY coatings were produced using the large-area pulsed electron-beam GESA facility. With a beam diameter of up to 10 cm, it is possible to treat large surface areas, with just a few overlapping electron beam pulses. The high cooling rates lead to nanocrystalline structures at the sample surface. Their oxidation properties were studied at 950 degreesC in air. As the surface treatment leads to smooth surfaces, with an R-A < 1.5 <mu>m, even on formerly rough low-pressure plasma spray (LPPS) samples, the samples can subsequently be coated directly with electron beam physical vapor deposition (EBPVD) thermal barrier coatings (TBC). The growth of the thermally grown oxide (TGO) on such samples was also studied at 950 degreesC in air for up to 5000 h and compared to that of samples without the TBC. The treated samples appeared to have a strongly enhanced oxidation resistance without spinel formation in the alpha -Al2O3 oxide scale. (C) 2001 Published by Elsevier Science B.V. All rights reserved.