Microstructure, impact and wear resistance of NiCu-based composite coatings with different WC content deposited by laser direct energy deposition

Tungsten carbide (WC), renowned for exceptional hardness, strength, and superior wettability with metal substrates, is a material widely used in the manufacture of metal matrix composite coatings. These properties enable WC to significantly enhance the hardness and wear resistance of coatings. However, the content of WC is a key factor influencing the microstructure and mechanical performance of the coatings. This study systematically investigates NiCu-based composite coatings with varying WC contents, which were deposited onto 42CrMo substrates by laser direct energy deposition (LDED). The objective was to evaluate the effects of WC content on the toughness and wear resistance of the coatings. The results reveal that the composite coatings are predominantly composed of gamma-Ni(Cu), WC, and W2C phases. With increasing WC content, the dilution effect of the substrate on the coating intensifies, concurrently improving the uniformity of WC particle distribution. Furthermore, the presence of WC influences the grain growth of the NiCu binding phase. Higher WC content enhances the fraction of high microhardness regions, enhancing wear resistance. However, excessive WC content results in stress concentration and crack propagation, which adversely affect the toughness and overall mechanical properties of the coatings. The optimal WC content was determined to be 45 wt%, demonstrating a favorable balance between impact toughness and wear resistance. These findings provide critical insights into the role of WC in improving the properties of NiCu-based composite coatings and provide valuable guidance for optimizing the application of coatings in mechanical components requiring durability and strength.