Nanomechanical and nanotribological characterization of multilayer self-lubricating Ti/MoS2/Si/MoS2 nanocoating on aluminium-silicon substrate

Ti/MoS2/Si/MoS2 multilayer coating was fabricated by a pulse laser deposition method from a titanium, molybdenum disulphide, and silicon targets, and the coating was deposited in layers on aluminium-silicon substrates, at room temperature. The structural analysis and surface morphology of multilayer Ti/MoS2/Si/MoS2 coating were analysed using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy integrated with energy dispersive X-ray spectroscopy. Nanomechanical tests were performed on Ti/MoS2/Si/MoS2 coating at small loads of 2000 to 6000 mu N to study the effect of load on hardness and Young's modulus. Nanoscratch and nanowear tests were conducted on Ti/MoS2/Si/MoS2 coating at a low load of 1000 to 5000 mu N and 100 to 500 mu N, respectively, to study deformation and failure behaviours of coating/substrate system and also their nanotribological properties. The results show that hardness and Young's modulus of Ti/MoS2/Si/MoS2 coating decrease with increase in load. A low friction coefficient of 0.09 to 0.16 was observed, which proves that the Ti/MoS2/Si/MoS2 coating possesses self-lubricating property. The wear rate of Ti/MoS2/Si/MoS2 coating increases 3.3 x 10(-10) to 7.8 x 10(-10) mm(3)/Nm with increase in load. Ti/MoS2/Si/MoS2 multilayer coating shows a smooth wear track with no cracks and debris on the surface, which attributed plastic flow of softer coating material around the wear track.