Heping Li,Zhiqiang Ke,Jing Li,Lihong Xue,Youwei Yan
Pores and cracks are usually inevitable in the coatings fabricated by plasma spraying . Herein, thermal chemical reaction technique was developed as an effective low-temperature strategy for addressing this issue. Dense α-Al 2 O 3 /AlPO 4 coating was synthesized on the surface of the plasma sprayed Al 2 O 3 -based coating by thermal chemical reaction at 500 °C. The α-Al 2 O 3 /AlPO 4 composites permeated into the coating and effectively filled up the pores and cracks inside. The sealed coating showed a uniform and dense morphology. The hydrogen permeation rate of the sealed coating sharply decreased by a factor of 15, which further confirmed its significantly improved compactness. In addition, the coating exhibited good thermal shock resistance and bond strength after sealing. Considering its low-temperature heat treatment, facile fabrication process and wide applicability, thermal chemical reaction method can be potentially used as a cost-saving strategy for sealing plasma sprayed ceramic coatings .
Jintao Wang,Du Hong,Xin Zhong,Liping Huang,Yaran Niu,Hong Li,Xuebin Zheng,Jinliang Sun
A study of abradable sealing coatings (ASCs) compatible with ceramic matrix composites (CMCs) is reported. Three kinds of bi-layer ASCs (YSZ, Yb 2 SiO 5 , and Yb 2 Si 2 O 7 ) with CaF 2 lubricant phase were deposited by atmospheric plasma spray (APS) technology, respectively, which possessed the capability to protect CMCs from degradation and alleviate thermal expansivity mismatch. The porosity of all three coatings was less than 10%, and theYSZ-CaF 2 and Yb 2 Si 2 O 7 -CaF 2 coatings possessed similar Rockwell hardness, which were smaller than the Yb 2 SiO 5 -CaF 2 coating. However, the Yb 2 Si 2 O 7 -CaF 2 coatings displayed excellent abradability in friction and wear tests at room temperature and 900 °C. Long-term oxidation tests were conducted at 1300 °C for 100 h, and the YSZ-CaF 2 coating cracked and spalled. The structures of the Yb 2 SiO 5 -CaF 2 and Yb 2 Si 2 O 7 -CaF 2 coatings remained intact. Ca 0.15 Zr 0.85 O 1.85 solid solution and CaSiO 3 phase were formed in YSZ-CaF 2 coating, while Ca 2 Yb 8 (SiO 4 ) 6 O 2 phase was generated in Yb 2 SiO 5 -CaF 2 and Yb 2 Si 2 O 7 -CaF 2 coatings. After thermal shock with 40 cycles at 1100 °C, the whole YSZ-CaF 2 coating spalled off, while the structure of Yb 2 SiO 5 -CaF 2 and Yb 2 Si 2 O 7 -CaF 2 coatings remained integrity with good thermal shock resistance. This study might offer new insights for the further development of ASCs suitable for CMCs.
危险品化学品经营许可证（带存储）