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3891 |
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Tribological performance of plasma sprayed Al2O3-Cr2O3 composite coatings against graphite under severe conditions |
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Kai Yang* / Shanghai Institute of Ceramics, Chinese Academy of Sciences, P.R. China Xiaming Zhou / The Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China, China Chenguang Liu/ The Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China, China Shunyan Tao/ The Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China, China Chuanxian Ding/ The Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China, China |
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Oxide ceramics exhibit high strength, high hardness and anti-wear performance, as well as high temperature and good oxidation resistances. The corresponding coatings show excellent potential in the dynamic seal system in the turbine pumps of the rocket engines with the combined working conditions of high temperature, high specific pressure, strong oxidation and thermal shock. However, low toughness of oxide ceramics restricts their practical applications. It is difficult to combine conventional toughening methods with plasma spraying technology. Cr2O3 and ±-Al2O3 possess the same crystalline structure. Cr3+ and Al3+ have the approximate ionic radiuses. Accordingly, Al2O3-Cr2O3 solid solutions are easily formed. Al2O3-Cr2O3 composite coatings were fabricated by plasma spraying. They possess better comprehensive mechanical and thermal conduction performances than Al2O3 and Cr2O3 coatings. The tribological properties of Al2O3, Cr2O3 and Al2O3-Cr2O3 coatings were tested using a block-on-ring arrangement under the high P and V(against the graphite). Based on the experimental results, the following conclusions can be drawn: (1) Compared with Al2O3 coating/graphite and Cr2O3 coating/graphite pairs, the friction coefficients of AC50(Al2O3-50wt.%Cr2O3) composite coating/graphite and AC90(Al2O3-90wt.%Cr2O3) composite coating/graphite pairs are more stable. The corresponding wear rates of the coatings and graphites are lower. (2) The friction surface temperature follows the sequence AC90 composite coating/graphite < AC50 composite coating/graphite < Al2O3 coating/graphite. The lower friction surface temperature is beneficial to the formation of more effective and stable graphite film on the coating. Therefore, the corresponding friction pairs would present better tribological properties. (3) AC90 composite coating/graphite pair show good anti-wear performance, which may be attributed to the relatively high thermal conductivity. |