Ni60+TiC等离子熔覆层的汽蚀特征

Cavitation erosion characteristics of Ni60+TiC plasma cladding layer

采用等离子熔覆技术在1Cr18Ni9Ti不锈钢表面制备了Ni60+TiC等离子熔覆层,采用磁致伸缩汽蚀仪对熔覆层的汽蚀特征进行了研究,并与ZG06Cr13Ni5Mo马氏体不锈钢进行了对比,为了探讨汽蚀发生发展的过程,采用SEM对汽蚀破坏进行了原位观察。结果表明:熔覆层的组织由TiC、γ-Ni固溶体及γ-Ni固溶体与硼化物的共晶体组成,这种复合熔覆层具有高的硬度(800 HV0.2),抗汽蚀性明显优于ZG06Cr13Ni5Mo钢。两者的汽蚀形貌相似,均具有"扁形形貌";Ni60+TiC等离子熔覆层的汽蚀破坏首先从γ-Ni基体与TiC陶瓷颗粒的界面开始,同时γ-Ni基体产生塑性变形、裂纹、碎裂,当其不再包覆TiC陶瓷颗粒时,TiC颗粒脱落;ZG06Cr13Ni5Mo马氏体不锈钢的汽蚀破坏起始于马氏体板条界。

A Ni60 ＋ TiC layer was prepared by plasma cladding technology on surface of 1Cr18Ni9Ti stainless steel. Microstructure of the cladding layer was investigated by X-Ray diffraction （XRD） and scanning election microscopy （SEM）. Resistance to cavitation erosion of the cladding layer was examined by cavitation erosion test on a vibratory cavitation apparatus and compared with that of hydro-machine material ZGO6Cr13Ni5Mo martensite stainless steel. In order to reveal the cavitation erosion process, in situ observation of cavitation erosion damage was proceeded on SEM. The microstructure of the layer consists of TiC particles, γ-Ni solid solution and eutectic of γ-Ni and compounds. The cladding layer with higher microhardness （800 HV 0.2）has better resistance of cavitation erosion than that of ZGOrCrl3Ni5Mo steel （260 HV 0.2）. The layer and ZGOrCr13Ni5Mo steel present a similar cavitation erosion morphology, namely, fiat pattern. It was found that the cavitation erosion of the cladding layer began at the interface of y-Ni matrix and TiC particles while plastic deformation, cracking and fracture took place in γ-Ni matrix. TiC particles fall off when γ-Ni can not clad them. The cavitation erosion of ZGO6Cr13Ni5Mo steel initiated at the lath interface of martensite.