Evaluating the performance of newly developed PVD-AlN-coated cermet tools in hard turning of AISI 4340 steel under dry and minimum quantity lubrication

Cermet cutting tools, owing to their superior mechanical strength and favorable tribological characteristics, have emerged as an effective solution for machining difficult-to-cut materials such as hardened steel, particularly under high-temperature cutting conditions. To further improve cutting performance, sustainable minimum quantity lubrication (MQL) has been widely adopted, as it supplies a controlled amount of lubricant directly to the deformation zone, effectively minimizing frictional heat generation and associated tool degradation. In this context, the present study evaluates the machining performance of cermet cutting tools under dry and MQL environments through a comprehensive analysis of surface roughness, cutting force, chip morphology, and tool life. Moderate to high-speed regime is selected, with cutting speeds ranging from 200 to 300 m/min, feed rates from 0.05 to 0.1 mm/rev, and a constant depth of cut of 0.1 mm. The experimental results demonstrate that MQL significantly enhances machining performance by reducing surface roughness up to 23.44%, and cutting forces up to 12.06%, while generating finer chip morphology and enabling more stable tool wear progression. Moreover, tool life under MQL was improved up to 30.58% due to its superior cooling and lubrication effectiveness compared to dry cutting. The economic analysis further revealed that MQL can reduce the total machining cost without compromising surface quality. Overall, the findings highlight the technical and economic advantages of MQL for improving machining efficiency and sustainability when using cermet tools.