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 o n MCrAlY coatings were produced using the large-area pulsed electron-beam G ESA 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 su rface 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 su bsequently be coated directly with electron beam physical vapor deposition (EBPVD) thermal barrier coatings (TBC). The growth of the thermally grown o xide (TGO) on such samples was also studied at 950 degreesC in air for up t o 5000 h and compared to that of samples without the TBC. The treated sampl es 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.