Effect of Transition Element Co on the Microstructure, Wear Resistance, and Oxidation Resistance of AlNbMoTa _0.5 Co _x Laser‐Clad Coatings

AlNbMoTa _0.5 Co _x coatings were successfully prepared on a titanium alloy substrate using laser cladding. The lattice distortion is particularly pronounced when the Co content is low. With a melting point significantly lower than that of the high‐melting‐point principal elements, Co segregates in the inter‐dendritic regions of the BCC solid solution. The size of these inter‐dendritic spaces gradually increases with higher Co content. Furthermore, Co forms a solid solution structure primarily composed of Co‐Al‐Ti with a Co‐HCP crystal structure in the inter‐dendritic areas. The addition of a small amount of Co leads to a significant decrease in the toughness of the clad coating, resulting in poorer wear resistance at room temperature. The wear resistance at room temperature slightly improves due to grain refinement. In terms of high‐temperature performance, the element Co enhances the high‐temperature properties of the coating by slowing down the oxidation rate of the dendritic constituent Ti. On the one hand, it improves the high‐temperature wear resistance of the clad coating by forming a thinner self‐lubricating layer on the worn surface. On the other hand, under high‐temperature oxidation erosion, it slows down the oxidation rate of the dendritic constituent Ti, thereby improving the high‐temperature oxidation resistance of the clad coating.