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

Abstract

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 c 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 c 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 c phase. In addition, the plasticity of this composite continuously improved as the eutectic phase disappeared and the c 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.

Effect of Post-Fabrication Heat Treatments on the Microstructure of WC-12Co Direct Energy Depositions

“…Some studies, such as [16,21,22], have demonstrated that the solid solubility of W in the Co matrix can be increased through an appropriate heat treatment process, which leads to both the strengthening of the Co phase and the increase in toughness of carbide particles up to a temperature of about 550 • C; above this temperature, the amount of carbides decreases and they transform into brittle structures. Chen et al [23] studied the effects of different annealing temperatures on the microstructural evolution and on the performance of WC-Co AM parts. The authors found that annealing temperatures in the range of 800-900 • C are sufficient to solubilize the η-phase and to improve the carbide distribution in the matrix.…”