Experimental assessment on machinability performance of CNT and DLC coated HSS tools for hard turning

The present work investigates the deposition of carbon nanotubes (CNT) over the HSS tool. Also, it assesses the machining capacity of the coated tool with respect to some of most important aspects of the machinability, such as surface roughness, cutting tool-tip temperature, cutting forces, tool wear, and service life. The Plasma Enhanced Chemical Vapour Deposition (PECVD) technique was used to deposit CNTs over the substrate. To recognize the dense deposition of CNTs, microstructural analysis was carried out through Scanning Electron Microscopy (SEM) and Raman spectroscopy. Further, a scratch test was embedded to validate the bonding strength of the covered layer substrate. Machining experiments were performed using CNT and Diamond-Like Carbon (DLC) coated tools. The analysis of experimental outcomes for three different cutting environments shows that the CNT coated tool represent a viable candidate for machining of harder materials. We have observed a dramatic reduction of the cutting tool tip temperature and cutting forces due to the excellent mechanical and thermal properties of CNTs. Indeed, the CNT coated tools prove their suitability when compared with the DLC coated tools. The analysis of tool wear demonstrated a much lower wear condition for CNTs tools when comparing to DLC coating one. This was translated in longer tool life for the CNT coated tool, which was about 28 min longer with only marginal failure under high cutting conditions when comparing to DLC one.