Study on microstructure and tribological properties of nano/micron TiC/TC4 composites fabricated by laser melting deposition

Laser melting deposition technology was used to fabricate TC4 alloy reinforced by micron TiC, nano TiC and nano/micron TiC ceramic particles. During the fabricating process, micron TiC was partially dissolved and nano TiC was completely dissolved, and TiCx phase was formed in situ in the three composites. The average grain size of TC4 alloy is 126.74 μm, the micron TiC/TC4 composite is 41.86 μm, the nano TiC/TC4 composite is 9.98 μm, and the nano/micron TiC/TC4 composite is 9.64 μm, and the complete dissolution of nano TiC significantly refines the β grains. The microstructure of the micron TiC/TC4 composite were composed of eutectic TiCx, primary TiCx, unmelted TiC and the nano TiC/TC4 composite were composed mainly of primary TiCx. A unique microstructure characteristic of primary TiCx growing along the edge of unmelted TiC was formed in the nano/micron TiC/TC4 composite. The microhardness and wear tests revealed that the nano/micron TiC/TC4 composite have the highest microhardness (528 HV 0.2 ) and the nano TiC/TC4 composite have the lowest wear rate (0.2166 mg/m). This paper provides a guidance for the study of microstructure evolution of nano/micron TiC synergistically reinforced TC4 alloy by laser melt deposition.