Influence of microstructure on the durability of gadolinium zirconate thermal barrier coatings using APS & SPPS processes

SURFACE & COATINGS TECHNOLOGY

卷:337

Article

Kumar, Rishi¹  Cietek, Drew¹  Jiang, Chen²  Roth, Jeffrey¹  Gell, Maurice¹  Jordan, Eric H.¹ 

[1] Univ Connecticut, Inst Mat Sci, 97 North Eagleville Rd, Storrs, CT 06269 USA

[2] HiFunda LLC, 270 Middle Turnpike, Mansfield, CT 06269 USA

关键词: Thermal barrier coatings;    TBC microstructure;    Gadolinium Zirconate;    Solution precursor plasma spray;    Air plasma spray;    CMAS resistance;   

DOI  :  10.1016/j.surfcoat.2018.01.004

来源: Elsevier

【 摘 要 】

Excellent CMAS resistance in Gadolinium Zirconate, Gd2Zr2O7 (GZO) coatings is attributed to vigorous reactions between the CMAS melt and the GZO that form secondary phases that rapidly crystallize and block further infiltration of CMAS. In this study, Gd2Zr2O7 (GZO) coatings were deposited using air plasma spraying (APS) and solution precursor plasma spraying (SPPS) processes. The relative performance of GZO in furnace thermal cycle tests with and without CMAS was determined. SPPS GZO TBCs showed 8 x longer lives in thermal cycling but 10 x shorter lives in CMAS testing, as compared to APS GZO TBCs. Superior performance of the SPPS coatings without CMAS can be attributed to characteristic stress relieving vertical cracks in the microstructure, which are absent in APS TBCs. These vertical cracks also act as channels to CMAS melt infiltration, which causes the loss of strain compliance and hence poorer CMAS resistance. X-ray diffraction of the failed SPPS GZO coatings revealed the formation of apatite phases, but the majority of vertical cracks were not sealed. The denser than typical APS coatings on the other hand effectively blocked the CMAS infiltration with CMAS arrest observed at a depth of similar to 25 mu m. The SPPS results suggest that the width of vertical cracks is an important parameter for sealing and hence impeding CMAS infiltration Sealing was observed in cracks with < 1 mu m in width. Wider cracks completely defeat the beneficial CMAS blocking behavior of GZO.

【 授权许可】

Free