Effects of Coating on Surface Recrystallization of DD6 Single Crystal Blades

Abstract:

The fully heat-treated DD6 single crystal turbine blades were treated in three ways: (1) surface grinding, without coating; (2) firstly surface grinding, then surface coated with HY₃(NiCrAlY) anti-oxidation coating; (3) after surface grinding, coated surface with the bond layer of NiCrAlY and top layer of YSZ(Y₂O₃ stabilize ZrO₂) for the double-layer thermal barrier coatings. All these three experimental blades were treated with vacuum heat-treatment at 1120°C for 4h. The effects of coating on surface recrystallization of single-crystal blades have been investigated. The results indicate that: just with surface polishing blade generated a 6~9μm thick cellular recrystallization zone on the surface. The γ' presented coarse morphology and distributed discretely within cellular, and the γ' growth direction was perpendicular to the cellular interface; blade surface coated with anti-oxidation coating after polishing formed a 3~6μm thick cellular recrystallization zone in the matrix interface. But the grain boundary was fuzzy and recrystallization morphology was incomplete; the matrix interface morphology of blade coated with thermal barrier coatings after polishing changed insignificantly, but some local cellular recrystallization was found. The results indicate that the coating changes the cellular recrystallization morphology of the original matrix of the blade, which can effectively reduce the occurrence degree of recrystallization.

• Periodical: Materials Science Forum (Volumes 747-748)
• Pages: 483-488
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.747-748.483
• Online since: February 2013
• Authors: Yu Liang Jia, Yun Song Zhao, Yu Shi Luo, Shuai Yang, Jian Wei Xu, Ding Zhong Tang
• Keywords: Coating, DD6 Single Crystal Superalloy, Surface Recrystallization, Turbine Blade

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