Microstructure And Mechanical Properties Of Micro/Nano Structured Composite Coatings On Ti-6Al-4V Prepared By Fiber Laser Cladding

In this paper, the micro/nano WC-Co particle reinforced composite coating with a thickness of about 1mm was prepared in the Ti-6Al-4V matrix by fiber laser. Microstructure of cladding layer and interface examined by means of optical microscope scanning（OM） and scanning electron microscope（SEM）. Phase compositions were analyzed by X-ray diffraction（XRD） and SEM-EDS. The microhardness and wear resistance were tested on HXD-1000 TMSC microhardness tester, HT-600 high temperature friction and wear tester. The effects of addition different carbides（Cr₃C₂, VC） on the microstructure, microhardness and wear resistance of micro/nano WC-Co composite coatings were studied. The results showed that:（1） No obvious pores and cracks were observed in the laser cladding micro/nano WC-Co composite coating, and the micro WC-Co composite coating has a lower dilution rate than the nano WC-Co composite coating.（2） The microstructure of the laser cladding micro/nano WC-Co composite coating was obviously refined by adding VC and Cr₃C₂. While adding VC and Cr₃C₂ coatings obtained organization finer and more uniform than adding VC or Cr₃C₂ individually. The main phases of the coating composition of Ti C, Ti2 Co, α-Ti,（Ti, W）C, Co3W3 C, W.（3） Adding different carbide（WC and Cr₃C₂）, a large number of Ti-W, Ti-W-C, Co-W-C and other solid solutions were appeared in laser cladding micro-nano tungsten carbide composite coatings, and the precipitation of W atoms was accompanied by the laser cladding.（4） Adding the same kind of carbide, the nano-tungsten carbide composite coating compared micron-tungsten carbide composite coating has higher microhardness, but also has better wear resistance. In contrast to the Ti-6Al-4V matrix material, its microhardness and wear resistance were significantly improved.