Influence of deep cryogenic cooling on tool wear and surface roughness of coated tungsten carbide inserts using statistical techniques

Abstract

Tool life enhancement with improved machining performance of existing turning inserts during hard turning process is an essential industrial requirement to reduce the manufacturing cost and to improve the surface finish with higher accuracy. The objective of this paper is to study the effects of Deep Cryogenic Cooling on coated tungsten carbide inserts and to evaluate their tool wear and resulting surface finish by conducting turning experiments on P20 tool steel material. To evaluate these properties, turning experiments were carried out as per the Taguchi’s design of experiments technique, by considering the three experimental parameters namely turning speed, depth of cut and feed rate. The effect of these parameters on tool wear and surface finish of the workpiece are analyzed by analysis of variance technique. The results indicated that feed rate had the highest influence of 71.85% on the surface finish of the machined surface, whereas the depth of cut influenced 14.86% & followed by turning speed which had 4.91% influence on surface finish. Similarly, for tool wear, it was found that turning speed had a significance value of 39.95% on tool wear followed by the depth of cut (37.95%) and feed rate (18.85%). The experimental data were used to develop the regression correlations for surface finish, and tool wear and confirmation tests were carried out to validate the models. The comparison between predicted and experimental values indicated a maximum deviation of around ±8% for surface roughness and ±11% for the observed tool wear. And scanning electron microscopic analysis of deep cryogenic treated inserts indicates a homogeneous distribution of η-carbides in cobalt matrix and a grain size refinement of α-phase compared to untreated inserts.