Chenglu Lian,Zhihua Long,Wei Qian,Zhichen Guan,Kun Huo,Yinqun Hua,Jie Cai
Thermal barrier coating materials play a crucial role ensuring the efficient and stable operation of gas turbines. The thermophysical and mechanical properties of GZ 1-x -GT x (x = 0, 0.1, 0.3, 0.5) composite ceramics, as well as the corrosion resistance properties against calcium magnesium aluminum silicate (CMAS) at 1250 °C, were investigated. The results indicated that the overall properties of Gd 2 Zr 2 O 7 -GdTaO 4 composite ceramics significantly improved with an increase in the second phase GdTaO 4 content. Among all the ceramics designed, GZ 0.5 -GT 0.5 exhibited the lowest thermal conductivity (0.920 W m −1 K −1 at 800 °C) and the highest fracture toughness (2.02 MPa m 1/2 ). Additionally, the molten CMAS interacted with the Gd 2 Zr 2 O 7 -GdTaO 4 composite ceramics, forming a dense apatite layer, which positively contributed to inhibiting CMAS infiltration. Considering its excellent thermal, mechanical, and corrosion resistance properties, Gd 2 Zr 2 O 7 -GdTaO 4 composite ceramics are considered a promising material for thermal barrier coatings.
Xinxin Wang,Zhihua Long,Wei Qian,Yunxia Ye,Fengze Dai,Yinqun Hua,Jie Cai
Tremendous efforts have been devoted to exploring alternative materials to 8 wt% yttria-stabilized zirconia used for thermal barrier coatings . In this work, novel composite ceramic GdPO 4 /GdTaO 4 was designed by introducing GdTaO 4 as second reinforcement phase into GdPO 4 matrix. Mechanical and thermophysical properties of resulting composites were studied as a function of doping concentration of GdTaO 4 . Results suggested GdPO 4 /GdTaO 4 composite ceramics consisting of GdPO 4 monazite and GdTaO 4 monoclinic phases, indicating GdPO 4 and GdTaO 4 with maintained excellent chemical compatibility at high temperatures. GdPO 4 /GdTaO 4 composite ceramics achieved superior hardness of 5.82 GPa, fracture toughness of 2.72 MPa m 1/2 , and thermal conductivity of 1.36 W•m −1 •k −1 at GT doping concentration of 50 wt% owing to grain refinement and scattering of phonons caused by the doped GdTaO 4 phase. In sum, excellent mechanical and thermophysical properties of GdPO 4 /GdTaO 4 composite ceramics look potential for thermal barrier coatings materials.
Because the CMAS corrosion and phase transformation at elevated temperatures above 1250 °C have limited the applications of traditional YSZ , the design of novel thermal barrier materials is a hotspot. GdTaO 4 is considered as a type of potential novel thermal barrier material owing to its low thermal conductivity . In this study, the mechanical and thermal properties, CMAS corrosion resistance , and the wettability of the GdTaO 4 were studied and compared with that of YSZ. The results show that the coefficient of thermal expansion and hardness of GdTaO 4 are 14.1 × 10 −6 K −1 (1350 °C) and 534.2 Hv 0.3 respectively. The thickness of CMAS reaction layer of GdTaO 4 is ~30.8 μm after 24 h reaction at 1350 °C, which is thinner than that of YSZ. After corrosion reaction, the CMAS glass aggregated instead of completely disappearing or continuously extending over the surface of GdTaO 4 . The main reaction product is Ca 2 Ta 2 O 7 , and the anorthite phase may not be detected, which is similar to YTaO 4 . By comparison, the dense substrate of YSZ became porous and CMAS glass has disappeared after 10 h. CMAS corrosion at 1350 °C. The on-line contact angle results show that the wettability of CMAS on GdTaO 4 is worse than that on YSZ at 1350 °C, while the opposite of the work of adhesion, which indicates that GdTaO 4 can remove liquid CMAS more easily than YSZ TBCs during the service. Furthermore, the corrosion depth and areas of GdTaO 4 are smaller than those of YSZ in the same situation. These findings suggest that GdTaO 4 possesses better high-temperature properties and CMAS corrosion resistance than YSZ as a kind of potential of thermal barrier material.
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