Design optimization of cutting conditions and analysis of their effect on tool wear and surface roughness during hard turning of AISI-H11 steel with a coated-mixed ceramic tool

The present study is an attempt to model the tool wear and surface roughness, through response surface methodology (RSM) (luring hard turning of AISI-H11 steel with TiN-coated-mixed ceramic inserts. The effect of machining parameters - i.e. cutting speed, feed rate, depth of cut, and workpiece hardness - on the response factors, viz. flank wear and surface roughness, have been investigated by applying analysis of variance (ANOVA) and through factor interaction graphs in the RSM. The non-linear quadratic models best fit the experimental data points. The desirability function approach has been used for multiple response factors optimization. The confirmation experiments carried out to check the validity of developed models predicted response factors within 5 per cent error. The feed rate, depth of cut, and workpiece hardness are observed to have a statistically significant impact on the flank wear, whereas feed rate and workpiece hardness are the significant factors affecting the surface roughness. The tool wear was monitored with a toolmaker's microscope, and wear characterization of some of the representative inserts was carried out using scanning electron microscope/energy dispersive X-ray (SEM-EDX) analysis. The tool appears to be worn out by abrasion, notch wear, and chipping of the tool surface owing to rubbing and impingement of hard particles in the work material and also by adhesion wear.