Surface integrity and tool life when turning of Ti-6Al-4V with coolant applied by different methods

The main focus of this study is to investigate the behaviour of cemented carbide tools and the surface integrity obtained when turning Ti-6Al-4V alloy. Machining trials were carried out with emulsion cutting fluid applied under conventional and high-pressure supplies and also in an argon-enriched environment. Tool life, cutting force, surface roughness, micrograph and microhardness beneath machined surface were evaluated for better understanding the relationship between the fluid environment and the surface integrity of the machined workpiece. Machining with high-pressure coolant supply generated the best tool life results, while enriched argon showed lower tool life because of the lower conductivity and poor lubrication characteristics of argon gas that lead to heat to be more concentrated at the cutting area, thus weakening the strength of the cutting tool and accelerating tool wear. No plastic deformation was observed on the machined surfaces under the conditions investigated. However, there was evidence of surface hardening after machining with conventional and in an argon-enriched environment due to the poor cooling function of argon. Surface hardening was minimal after machining with high-pressure coolant supplies.