Wear behavior of PVD TiN coated carbide inserts during machining of Nimonic 90 and Ti6Al4V superalloys under dry and MQL conditions

This paper mainly deals with the tool wear characteristics of PVD TiN coated carbide inserts during turning of two aerospace alloys (Nimonic 90-Ni based alloy and Ti6Al4V- Ti based alloy). To fulfill the sustainability criteria the experiments have been conducted under dry and minimum quantity lubrication environment (MQL). To further enhance the effectiveness of MQL the specially prepared biodegradable emulsion of sunflower oil in water has been used as the cutting fluid. For better understanding of the cutting characteristics the same set up is employed for both the aerospace alloys. Due to high chip tool contact during machining of Nimonic 90, more intense nose wear has been observed over the cutting inserts. High strength of Nimonic 90 as compared to Ti6Al4V also resulted in high notch wear over the tool inserts during turning. The use of biodegradable emulsion under MQL mode has produced better results for Ti6Al4V. The attributes like good wettability and high penetration provided significantly less flank wear and rake wear during machining of Ti alloy under MQL condition. Furthermore due to the controlled wear during turning of Ti6Al4V, the cutting forces were found to be stable and significantly low as compared to Nimonic 90.