Microstructures and properties of nano-modified multimodal Cr₃C₂-NiCr coatings made through laser cladding

Both the nano-modified multimodal and conventional Cr₃C₂-NiCr coatings were fabricated by laser cladding (LC) on a CuCrZr alloy substrate with a stainless steel transition layer. The study investigated the microstructural evolution of the coatings during the LC process. The effect of the stainless steel transition layer between the substrate and coatings on microstructure, microhardness, and wear resistance was discussed. Many aggregates formed by the aggregation of micron or large-size submicron particles contain many cavities, which are filled by small-size or nano-ceramic particles during the laser cladding process to improve the density of the coatings and properties. Different from other LC coatings, only micro-melting occurred in the bonding zone between the coatings and transition layer, but no apparent melting phenomenon appeared, which may be due to the high content of Cr₃C₂ ceramic phase and low content of NiCr adhesive phase in the coatings. The Cr₃C₂-NiCr coatings, transition layer, and copper (Cu) substrate are seamlessly integrated and compatible, ensuring effective interface formation without any discernible cracks. The nanostructure multimodal Cr₃C₂-NiCr coating showed significantly higher average microhardness values of 1357 HV_0.3 than conventional Cr₃C₂-NiCr, 1184 HV_0.3. Furthermore, careful parameter selection led to outstanding wear-resistant nano-modified multimodal Cr₃C₂-NiCr, paving the way for future industrial applications.