Microstructural Transformation and Tribological Properties of Laser-Cladded FeNiCoCrTi0.5-xNbC High-Entropy Alloy-Based Composite Coatings

Laser-cladded FeNiCoCrTi0.5-xNbC (x = 3 wt.%, 6 wt.%, 12 wt.%, and 24 wt.%) high-entropy alloy-based composite coatings (HACCs; donated as C1, C2, C3, and C4, respectively) without pores, cracks, and spherical adhesion are successfully prepared and metallurgically deposited on 45 steel. It is found that the as-prepared composite coatings are mainly composed of body-centered cubic (BCC) solid solution and carbides. The increase of the NbC content in FeNiCoCrTi0.5-xNbC promotes the transformation of carbides from TiC to NbC, which causes carbides morphology to change from near spherical to polygonal and the carbides size to undergo a process of first decreasing and then significantly increasing. With the increase of the NbC content, the microhardness and wear resistance of FeNiCoCrTi0.5-xNbC first increase and then decrease. An appropriate amount of NbC can help FeNiCoCrTi0.5-xNbC HACCs resist friction and effectively protect the substrate. However, excessive NbC increases the local brittleness of FeNiCoCrTi0.5-xNbC and deteriorates the wear resistance.