Development of a Cu/MoS2/Ni Self-Lubricating Composite Clad through Laser Additive Approach over a Ti6Al4V Substrate and Its Characterizations

Solid lubricant coatings play a critical role in enhancing the tribological properties of engineering materials, particularly in aerospace and biomedical applications. Ti6Al4V is widely used in aerospace and defense industries due to its excellent mechanical properties and high strength-to-weight ratio. In this regard, a solid lubricant metal matrix composite (MMC) clad was successfully fabricated over Ti6Al4V. A full factorial (L16) was successfully implemented to investigate the interaction of process parameters for laser power and scanning speed with response outputs, such as the clad layer thickness and microhardness. The microstructural study of the clad confirmed the presence of dark and bright phases of the microstructure with cylindrical, elliptical, and lamellar structures. This showed the presence of molybdenum and sulfide phases (MoS2, TiS, CuS) and the presence of a nickel phase (TiNi, NiS, CuNi), confirmed through X-ray diffraction (XRD) analysis and energy-dispersive X-ray (EDX) spectroscopy; these phases bestowed hardness as well as solid lubricating properties on the clad. The microhardness of the clad was found to be 2-3 times that of the substrate material. The wear behavior of the clad was studied in the load range of 5-15 N; the coefficient of friction (0.33 for clad and 0.5 for base), wear track depth profile, and wear mechanism revealed that the cladded sample has higher wear resistance as compared to the substrate material. The worn morphology showed that microcutting and microplowing are the major phenomena of wear occurrence. Further, X-ray photoelectron spectroscopy (XPS) analysis was performed to determine the binding energy of the compound formed at the clad zone, which can predict the most significant phase for the alteration of the mechanical behavior of the solid lubrication clad.