Study on Thermal Insulation Performance and CMAS Hot Corrosion Resistance of Gd-Sc(Yb)-YSZ Ceramic Coatings
A two-step hydrothermal method was used to prepare two kinds of ceramic powders containing semi-hollow spheres with chemical composition of Zr0.87Y0.07Gd0.02Sc0.04O1.94(Gd-Sc-YSZ)and Zr0.87Y0.08Gd0.03Yb0.02O1.94(Gd-Yb-YSZ),respectively.The above ceramic powders were granulated and coated by atmospheric plasma spraying on the surface of the Al-permeated coating,to prepare two kinds of ceramic layers and form ceramic layer/Al-permeated layer/NiCrAlY/DZ40M thermal barrier coatings.The thermal insulation temperature at the heat source temperatures of 1 050℃ and 1 400℃ and CMAS hot corrosion resistance at 1 250℃ of the two kinds of thermal barrier coatings and the traditional YSZ coating were tested.The results demonstrates that both the Gd-Yb-YSZ and Gd-Sc-YSZ coatings remain intact and do not peel off after thermal insulation at 1 400℃ for 6 h.The two coatings are primarily composed of a metastable tetragonal phase(t'-ZrO2),which indicates that both the Gd-Yb-YSZ and Gd-Sc-YSZ coatings are expected to serve at 1 400 ℃ for a long term.At the high temperature,the Al-permeated layer plays a crucial role in maintaining the bonding stability of the ceramic layer on the surface of NiCrAlY alloy.The thermal insulation temperature of Gd-Yb-YSZ and Gd-Sc-YSZ coatings is higher than that of YSZ coating at the heat source temperatures of 1 050 ℃ and 1 400 ℃ .Furthermore,their thermal conductivities are only 0.35～0.5 times that of YSZ coating.It can be concluded that doping with Gd,Yb and Sc significantly en-hances the thermal insulation effect of the YSZ coating.Following exposure to hot corrosion of CMAS at 1 250 ℃ for 1 h,the edges of the YSZ coating exhibits peeling,whereas the centre of the Gd-Yb-YSZ coa-ting only becomes rough and the Gd-Sc-YSZ coating remains intact after 6 h.The CMAS hot corrosion re-sistance of the Gd-Sc-YSZ and Gd-Yb-YSZ coatings is much better than that of the YSZ coating,particular-ly for the former.
Gd-Sc(Yb)-YSZ ceramic coatingAl-permeated coatingthermal insulation temperaturether-mal conductivityCMAS hot corrosion
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