Microstructural Evolution and Tribological Performance of Laser-Cladded NiCrBSi/WC Composite Multilayer Coatings: Influence of Laser Energy Density and Powder Feed Rate

Abstract Unlike mono-layer claddings, the deposition of multilayer composite claddings involves fundamentally different and more complex thermal and metallurgical mechanisms due to cumulative heat input, altered interfacial boundary conditions, and evolving microstructural heterogeneity across successive layers. In industrial repair and remanufacturing applications, where processed components are often expensive, and the topmost layer governs functional performance, understanding the tribological behavior of the successively deposited layers is critically important. In this study, the microstructural evolution and dry-sliding wear performance of laser-cladded NiCrBSi/WC multilayer coatings deposited on AISI 316L stainless steel were systematically investigated. Microstructural characterization was performed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD), and hardness variations were evaluated across the cladding depth. Dry-sliding wear tests were conducted under identical conditions using a ball-on-disk configuration. The results reveal that laser processing parameters significantly influence WC dispersion, matrix continuity, and hardness stability in the second layer, which in turn governs tribological performance. The specific wear-rate varied by approximately fourfold, ranging from 2.26 × 10−5 to 9.15 × 10−5 mm3/(N m). Optimal tribological performance was achieved at an intermediate laser energy density of 72 J/mm2 with a powder feed rate of 15 g/min, corresponding to homogeneous WC dispersion, stable hardness gradients, and mild abrasive wear. In contrast, insufficient or excessive energy input resulted in carbide pull-out, matrix softening, or severe delamination. The findings highlight the necessity of layer-specific process optimization for reliable multilayer laser cladding of high-cost components.