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核电站汽轮机末级叶片因水蚀损伤,其表面形成微裂纹,在应力作用下叶片容易发生开裂,形成机组安全运行隐患。对比分析了常规火电及核电汽轮机运行蒸汽环境的不同,在此基础上,采用超音速火焰喷涂在0Cr17Ni4Cu4Nb(17-4PH)合金表面制备NiCr-Cr_3C_2抗水蚀层。采用扫描电镜观察涂层形貌,测试了涂层的硬度及耐冲蚀性。研究了抗水蚀涂层直接替代司太立用于17-4PH基材的可行性及此工艺用于修复叶片的可行性,并进行了现场模拟喷涂。结果表明:17-4PH合金表面超音速火焰喷涂抗水蚀涂层性能满足要求,可反复喷涂,在核电汽轮机末级叶片中的应用具有可行性。
Due to water erosion damage to the last stage blades of the turbine of a nuclear power plant, micro-cracks are formed on the surface of the turbine blades. Cracking of the blade is apt to occur under the action of stress to form a potential safety hazard of the unit. The differences of steam environment between conventional thermal power plants and nuclear power turbines were analyzed. Based on this, NiCr-Cr_3C_2 corrosion resistant coatings were prepared on the surface of 0Cr17Ni4Cu4Nb (17-4PH) alloy by supersonic flame spraying. The morphology of the coating was observed by scanning electron microscopy and the hardness and erosion resistance of the coating were tested. The feasibility of applying anti-water-erosion coating to 17-4PH substrate directly by Stearic acid and the feasibility of using this technology to repair the leaves were also studied. In-situ simulated spraying was also conducted. The results show that the performance of supersaturated flame sprayed water-repellent coating on 17-4PH alloy can meet the requirements and can be sprayed repeatedly. It is feasible to use it in the last blade of nuclear power turbine.