Performance Evaluation of a Hard Composite Solid Lubricant Coating When Dry Machining of High-carbon Steel

Abstract

ABSTRACTA novel hard composite solid lubricant coating combining TiN and MoSx has been developed using pulsed DC closed-field unbalanced magnetron sputtering (CFUBMS). The tribological and mechanical properties together with their interdependencies with the coating microstructures have been assessed and reported elsewhere. This article evaluates the machining performance and correlates the underlying tribological aspects of different TiN-MoSx coating architectures (deposited at titanium (Ti) cathode currents of 1, 3.5, and 5 A) when dry turning AISI 1080 high-carbon steel. A comparative performance study clearly established the supremacy of the composite coating (deposited at 3.5 A Ti cathode current with ∼12 wt% of MoSx) with a hard TiN underlayer over monolayer TiN, MoSx, and other related coating architectures in terms of cutting force, tool wear, and workpiece surface roughness. The superlubricity behavior of the said composite coated tool resulted in a reduction of cutting force (by up to ∼45% compared to the uncoated tool) and exhibited a tool life of 8 min, which was eight times and more than two times longer than that of the uncoated and conventional hard TiN coated counterparts, respectively. The workpiece surface roughness, Ra, also decreased by 13 to 21% when machined with the TiN-MoSx coated tool in comparison to the uncoated cemented carbide.