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

摘要

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 degrees 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 M7C3, M2C, and a small amount of the gamma phase. However, after PHT at a certain temperature (e.g., 700 or 800 degrees C), the eutectic phase gradually disappeared, and carbides, such as M7C3 and M2C, tended to be distributed uniformly in the gamma matrix, which improved the flexural strength of the composite. Nevertheless, after the PHT at 900 degrees C, the flexural strength of the composite displayed a downward trend, which was mainly because of the severe softening of the gamma phase. In addition, the plasticity of this composite continuously improved as the eutectic phase disappeared and the gamma phase softened. Based on the above results, we proposed a PHT at 800 degrees C for 1 h as an optimal process for this WxC + Ni-based composite.