Investigating the self-lubricating properties of novel TiSiVN coating during dry turning of Ti6Al4V alloy

Abstract

The machining of titanium alloys like Ti6Al4V has been challenging owing to their low thermal conductivity, making them highly difficult-to-cut. Many techniques have been adopted to improve machinability of Ti6Al4V titanium alloy and the durability of the cutting tools during its machining. Thus, to improve their machinability, the current work investigates the applicability of TiSiVN self-lubricating coating deposited on Al2O3–SiC ceramic cutting tools during continuous turning of Ti6Al4V alloy under dry cutting environment. The TiSiVN coating accounted for lower surface roughness and cutting temperatures under all conditions. Due to the formation of V2O5 at high temperatures that were observed during oxidation and machining tests in EDS and Raman spectroscopy, the TiSiVN coating helped in reducing friction and, thus, retained the crater wear area. In contrast, the worn area on the crater surface reduced for uncoated and TiSiN coated cutting tools due to a significant increase in nose depth decrement with increasing cutting speed. Furthermore, increased nose depth decrement resulted in the drop of machining forces when using TiSiN coated and uncoated cutting tools. However, the coating delamination due to oxidation was apparent which reduced the effectiveness of lubricious phases present in the cutting zone for TiSiVN coated tool.