Influences of plasma arc remelting on microstructure and service performance of Cr3C2-NiCr/NiCrAl composite coating

This work studies the influences of plasma arc remelting on the microstructure and properties of thermal sprayed Cr3C2-NiCr/NiCrAl composite coating. The microstructure and composition are analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The microstructure and density of the coating are modified after remelting. It is found that the amounts of the Cr23C6 and Cr2O3 phases of the remelted coating are increased compared with the as-sprayed coating. Based on the experimental results, the coating adhesion, microhardness and wear resistance are all enhanced through plasma arc remelting with limited power (below 42 kW). Specifically, the adhesion is improved due to the enhancement of the element diffusion near the interface and metallurgical bonding between the functional and bonding layer. In addition, the increase of microhardness is attributed to the decrease of porosity and the formation of secondary carbides and eta phase. However, remelting with excessive powers (above 42 kW) results in the delamination of the mechanical joint between the bonding layer and substrate, which has adverse effect on coating adhesion as well as the wear resistance. Therefore, the proper usage of plasma arc remelting is an effective approach to enhance the properties of the thermal sprayed Cr3C2-NiCr/NiCrAl composite coating.