Oxidative durability of TBCs on Ti2AlC MAX phase substrates

SURFACE & COATINGS TECHNOLOGY

卷:285

Article

Smialek, James L.¹  Harder, Bryan J.¹  Garg, Anita¹ 

[1] NASA, Glenn Res Ctr, Cleveland, OH 44135 USA

关键词: MAX phases;    Thermal barrier coatings;    Oxidation;    Spallation;    Alumna scales;   

DOI  :  10.1016/j.surfcoat.2015.11.018

来源: Elsevier

【 摘 要 】

Air plasma spray (APS) and plasma-spray-physical vapor deposition (PS-PVD) yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC), similar to 80-100 mu m thick, were produced on a commercial Ti2AlC MAX phase compound. They were oxidized in interrupted furnace tests for 500 h each, at five successive temperatures from 1100 degrees-1300 degrees C. The APS coating survived 2400 accumulated hours, failing catastrophically after 500 h at 1300 degrees C Porosity, large cracks, sintering, and high monoclinic YSZ phase contents were seen as primary degradation factors. The PS-PVD coating remained completely intact over 2500 total hours (65 cycles) including 500 h at 1300 degrees C, exhibiting only fine porosity and microcracking, with less monoclinic. These Ti2AlC systems achieved a minimum alpha-Al2O3 scale thickness of 29 and 35 mu m, respectively, as compared to similar to 6 +/- 2 mu m on average at failure for conventional bond coats on superalloys. Accordingly, times predicted from thermogravimetric analyses (TGA) of oxidation kinetics project an improvement factor of similar to 25-50x for the time to achieve these scale thicknesses at a given temperature. Extreme oxidative TBC durability is achieved because the thermal expansion coefficient of Ti2AlC is only slightly different than those for alpha-Al2O3 and YSZ. The strain energy term driving scale and TBC failure is therefore believed to be fundamentally diminished from the large compressive stress produced by higher expansion superalloys. Published by Elsevier B.V.

【 授权许可】

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