Influence of methane flow ratios on the structural and mechanical properties of Ti-doped diamond-like carbon films

Abstract

Diamond-like carbon lms with Ti dopant (Ti-DLC) are synthesized by reactive magnetron sputtering using a pure Ti metal target. This study determines the effect of methane ow ratios [R m =CH 4 /(Ar + CH 4 ), ranging from 4 to 12%] on the surface morphology, microstructure, mechanical properties and cermet cutting tool inserts features of Ti-DLC lms. The GIXRD diffraction spectrum for Ti-DLC lm depicts an amorphous structure. There are peaks for nano-crystalline TiC at 2θ values of 35.88 o , 41.52 o and 60.14 o , which respectively correspond to the (111), ( 200) and ( 220) planes of the face centered cubic structure.The characteristic binding energy of C 1s, Ti 2p and O 1s for Ti-DLC lm is determined using a highresolution XPS spectra. Increasing R m ow ratio (reducing Ti metal doping) increases the intensity of the Raman spectrum because there is an increased sp 2 -C (sp 2 /sp 3 ratio) site fraction for DLC components. The experimental results show that the hardness of the DLC lm increases from 11.07 GPa to 14.76 GPa as the R m ow ratio is increased from 4% to 12%. The adhesive strength of the Ti-DLC lm coating is measured using a scratch test and shows that the lm adheres well to the substrate. The Ti-DLC lms are coated onto cutter inserts for the dry milling of an Inconel 718 workpiece and the results show that all coated tools have a signi cantly longer tool life than uncoated tools.