Pulsed electron beam treatment of MCrAlY bondcoats for EB PVD TBC systems part 2 of 2: Cyclic oxidation of the coatings

This paper discusses the effect of pulsed electron beam (PEB) treatment of thermal sprayed MCrAlY bondcoats on the cyclic life of thermal barrier coatings (TBCs). Standard MCrAlY bondcoats were produced via HVOF, VPS and LPPS thermal spray methods. Some of the HVOF and VPS coatings were then given a PEB treatment before all the samples were coated with an EB PVD 7-8 wt.% yttria partially stabilized zirconia topcoat. The samples were all tested under cyclic oxidation conditions at 1150 °C with 1 h at temperature and 15 min cooling, samples were removed after 20% coating spallation and prepared for cross sectional analyses. testing revealed that although the PEB treatment had no measurable effect on the VPS sprayed samples, the HVOF coatings showed a significant increase in the cyclic life after the PEB treatment. The effect of the PEB treatment on the various samples is discussed as well as its effect on TGO growth morphology. PEB treatment of the HVOF bondcoat was found to reduce the rate of alumina growth and to suppress the formation of oxide pegs resulting in a smoother bondcoat interface.