Effect of Post-Heat Treatment on the Microstructure and Mechanical Properties of Laser-Deposited WxC + Ni-Based Composite Thin Walls

This paper reports the effect of post-heat treatment (PHT) on laser-deposited WxC + Ni-based composite thin walls. The PHT at 700, 800, and 900 °C was conducted to modify the microstructure and mechanical properties of the composite. The results showed that the as-deposited composite had a weak flexural strength and plasticity due to the brittle nature of the eutectic phase. The eutectic phase consisted of M(7)C(3), M(2)C, and a small amount of the γ phase. However, after PHT at a certain temperature (e.g., 700 or 800 °C), the eutectic phase gradually disappeared, and carbides, such as M(7)C(3) and M(2)C, tended to be distributed uniformly in the γ matrix, which improved the flexural strength of the composite. Nevertheless, after the PHT at 900 °C, the flexural strength of the composite displayed a downward trend, which was mainly because of the severe softening of the γ phase. In addition, the plasticity of this composite continuously improved as the eutectic phase disappeared and the γ phase softened. Based on the above results, we proposed a PHT at 800 °C for 1 h as an optimal process for this WxC + Ni-based composite.