激光熔覆Ni60-WC+TiC复合涂层的组织和性能

Microstructure and properties of Ni60-WC + TiC composite coating

采用激光熔覆工艺在TC4钛合金基体上制备了Ni60-25%WC+10%Ti C复合涂层,并通过场发射扫描电镜(FESEM)、XRD,摩擦磨损试验分析研究了熔覆层的组织和性能。结果表明,熔覆层中主要以树枝状晶为主,在1200 W时熔覆层中出现了一些块状组织,XRD分析表明,熔覆层中产生了Ti C、WC、VC等陶瓷相,另外还形成了Al Ni3、Al0.96B0.04Ni3、Cr2Ti以及C0.12Fe1.88金属化合物,这些相对于提高熔覆层表面硬度非常有利。硬度测试结果表明,熔覆层最高硬度可达1176 HV0.3,比基体硬度提高了322%。摩擦磨损结果表明,在1000 W时由于WC、Ti C等颗粒未熔,导致摩擦过程中硬质颗粒脱落,其摩擦因数甚至高于基体。而随着功率的增大,WC和Ti C等熔化、重新形核并长大,这些硬质相不易脱落,因此其摩擦因数更小,分别是0.18和0.10。

Ni60-25%WC +10%TiC composite cladding layers were prepared on TCA titanium alloy by using laser cladding technique,then the microstructure and properties of the cladding layers were studied by means of field emission scanning electron microscopy ^(FESEM),X- Ray diffraction (XRD)and frictional wear testing.The results show that dendritic crystal is the main crystal type in the cladding layer,and sonic bulk type crystals appear in.the cladding layer formed at 1200W power.The XRD results show that some of the ceramic phases such as TiC, WC and VC are found in the cladding layers,some intermetallie compounds such as A1Ni3,A10.96B0.04Ni3,Cr2Ti and CoA2Fe1s8 are also found, which benefits to improve the hardness.The hardness test results show that the hardness of the cladding layers is about 1176 hv0.3,as high as 322% of that of the substrate.The friction coefficient is even higher than that of the substrate,mainly because that some of unmelted TiC and WC strengthening particles fall off from cladding layers.With the increase of the laser power,WC and TiC particles melt,re-nucleation and growth,and these hard phases are not easy to fall off,the friction coefficient is decreased to 0.18and 0.10,respectively.