The Effect of CeO2 Content on the Microstructure and Properties of TiC/WC/Co Composite Cladding Layers

To address the issue that the insufficient surface hardness and wear resistance of ductile iron under harsh working conditions are likely to lead to early failure, using a cladding layer with dual hard phases is an effective method to improve the surface properties. However, the issue that a large amount of hard phases decompose under the action of a high-energy laser to generate brittle phases in the microstructure is quite troublesome. Therefore, by adding CeO2 to the cladding layer, a TiC/WC/Co composite cladding layer containing CeO2 is prepared on the substrate by means of a fiber laser. Through OM, SEM-EDS, XRD, and Rockwell hardness tests, the effects of the CeO2 content on the microstructure, phase composition, and hardness of the coating were studied to determine the optimal addition amount. The results show that the secondary dendrite arm spacing (SDAS) of the γ-Co phase and the sizes of TiWC2 and WC dendrites exhibit a non-monotonic trend of first decreasing and then increasing with the increase in the CeO2 content, and the morphology of TiWC2 evolves from a cross shape to a granular shape and then to a dendritic shape. When the CeO2 content is 2 wt.%, the WC dendrites are completely inhibited, and the SDAS of γ-Co reaches the minimum value; when the content increases to 4 wt.%, WC dendrite coarsening occurs, and at the same time, the γ-Co dendrite packing density increases significantly, and the eutectic fraction decreases obviously. The hardness of the coating first increases and then decreases with the increase in the CeO2 addition amount, and reaches a peak value of 91.4 HRC when the CeO2 content is 4 wt.%, which is approximately 2.57 times the hardness of the substrate.