On Deposition and Characterisation of TiN-WS₂ Composite Coating and Its Performance Evaluation in Dry Machining of AISI 1060 Steel

Abstract

Hard-lubricious composite coating consisting of hard TiN phase and soft lubricious WS₂ phase were deposited with a hard TiN under layer on steel discs, high speed steel blocks and ISO K10 grade tungsten carbide inserts. For comparison, pure TiN coatings were also deposited on the same substrates. Pulsed DC Closed Field Unbalanced Magnetron Sputtering was employed for the deposition of the coatings. The coatings were characterised with energy dispersive X-ray microanalysis, grazing incidence X-ray diffraction, field emission scanning electron microscopy, scratch adhesion test, nanoindentation test and pin-on-disc tribological test. The multilayered coating consisting of TiN-WS₂ top layer with TiN under layer showed greater adhesion with the substrate and less friction coefficient as compared to pure TiN coating. The machining test conducted on AISI 1060 steel revealed that the tool coated with TiN-WS₂ composite coating with TiN under layer exhibited the least cutting forces (axial, radial and tangential components) not only in comparison to the uncoated carbide tool but also in comparison to the TiN coated tool in the experimental cutting speed domain of 30–230 m/min because of the lubricious action of the WS₂ phase present in the top TiN-WS₂ layer. Tool life tests conducted at the highest cutting velocity of 230 m/min with feed of 0.2 mm/rev and depth of cut of 2 mm also revealed the superior performance of the (TiN-WS₂) on TiN coated tool as the multilayer coating could effectively slow down the growth of crater and flank wear respectively by facilitating easier sliding of chip over the tool rake surface and generation of lesser tangential cutting force.