超音速火焰喷涂Cr3C2/NiCr涂层抗加沙空蚀性分析
Analysis of silt cavitation erosion resistance of Cr3C2/NiCr coating prepared by high velocity oxy-fuel thermal spraying
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摘要: 采用HVOF技术在1Cr18Ni9Ti不锈钢基体上制备了Cr3C2/NiCr涂层,借助XRD,TEM,SEM等方法分析了涂层的组织形貌及相组成.以1Cr18Ni9Ti奥氏体不锈钢作为对比材料,用磁致伸缩空蚀仪配备扬沙装置测试了涂层在清水以及含沙水中抗空蚀性能.结果表明,涂层呈层状结构,含有未熔颗粒和少量孔隙,涂层由Cr3C2,Cr7C3,Cr23C6及NiCr等相组成;在清水试验中,1Cr18Ni9Ti不锈钢抗空蚀性能良好,与空蚀过程中1Cr18Ni9Ti奥氏体不锈钢产生加工硬化有直接关系;在含沙40 kg/m3试验水中,Cr3C2/NiCr涂层呈现出较好的抗空蚀性能,与涂层自身相组成以及较高硬度有关.Cr3C2/NiCr涂层破坏总是从孔隙等薄弱环节开始,而1Cr18Ni9Ti奥氏体不锈钢的破坏起始于晶界和孪晶界.Abstract: A Cr3C2/NiCr coating was prepared on 1Cr18Ni9Ti stainless steel by high velocity oxy-fuel (HVOF) thermal spraying. Phases and microstructures of the coating were analyzed by X-ray diffraction (XRD),transmission electron microscope (TEM) and scanning election microscopy (SEM),respectively. The cavitation erosion resistance and silt erosion resistance of the coating were evaluated under two experimental conditions (fresh water and water contained fine silt),and compared with hydro machine material 1Cr18Ni9Ti stainless steel. The result shows that the coating shows a layered structure and contains un-melted particles and some pores. The phases of the coating are composed of Cr3C2,Cr7C3,Cr23C6 and NiCr. The 1Cr18Ni9Ti stainless steel produces the work hardening,which results in the resistance to cavitation erosion. The Cr3C2/NiCr coating exhibits significantly higher microhardness than 1Cr18Ni9Ti stainless steel,which leads to the resistance to silt erosion of the coating. The mass loss of the coating usually happens at the edges of the pores while the cavitation damage of the 1Cr18Ni9Ti stainless steel happens at the grain boundary and twin boundary.