水轮机金属材料及其涂层抗空蚀和沙浆冲蚀研究进展

空蚀和沙浆冲蚀是对包括水轮机在内的水力机械过流元件产生破坏,进而降低其服役寿命的两种主要破坏形式。采用特定的工艺在水轮机过流元件基体材料表面沉积涂层,以提高元件的抗蚀性能受到越来越多的关注。综述了水轮机常用金属材料和近年来国内外研究人员对水轮机材料及其涂层空蚀和冲蚀失效机理的研究进展,针对国内外文献报道中采用的超音速火焰喷涂、激光熔覆、物理气相沉积和化学气相沉积等工艺制备的涂层的抗空蚀和沙浆冲蚀性能进行了重点论述。依据材料性质对文献中出现的表面强化材料进行分类,即合金材料、陶瓷材料、复合材料、金属玻璃材料和类金刚石材料五类,结合涂层制备工艺对各类涂层失效机理进行剖析。通过案例重点讨论了涂层的微观缺陷,如孔隙、裂纹、未熔颗粒,涂层的硬度,涂层与基材的结合强度,涂层的厚度等因素对抗蚀性能的影响。最后对其研究和应用现状,从工艺方法和材料两方面提出了展望,指出运用先进涂层技术和新型涂层材料制备高效涂层,是解决复杂多相流条件下空蚀和冲蚀联合问题的有效途径。

Research Progress of Cavitation and Slurry Erosion Resistance of Metal Materials and Coatings of Hydro Turbine

Cavitation and slurry erosion are two major damages to the overflowing components of hydraulic machinery including hydro turbine, which can reduce its service life. Depositing coating on the surface of substrate materials of overflowing components by using specific techniques to improve the erosion resistance has aroused increasing concern. The common metal materials of hydro turbine and the research progress concerning hydro turbine materials as well as corresponding cavitation and erosion failure mechanism by domestic and overseas researchers were reviewed in this paper. The cavitation and slurry erosion resistance of coatings prepared by untilizing high velocity oxy fuel spray (HVOF), laser cladding, physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods adopted in domestic and overseas published literatures were mainly discussed. In accordance with material properties, the surface strengthening materials in the literatures were categorized into alloy materials, ceramic materials, composite materials, metallic glass materials and diamond like materials. The failure mechanisms of various coatings were analyzed by combining with the coating preparation process. Effects of micirodefects in the coatings such as pores, cracks, unmelted particles, hardness, bonding strength between substrate and coating, thickness on erosion resistance were discussed based on cases. Finally, expectations about manufacturing technology and materials were proposed in respect of current research and application status. It is pointed out that the effective way to resolve the combined cavitation and slurry erosion under the complex multi phase flow conditions is preparing efficient coatings by making use of advanced coating technologies and new coating materials.