Performance evaluation of coated cermet insert in hard turning

Abstract

Cermet comprises of a ceramic matrix, which is bonded through a metallic binder. The addition of metal coating layers enhance the toughness as well as the thermal resistance of the ceramic. Cermet is mainly recommended for chemical-resilient, high-temperature applications and as insulators. However, current work emphasized on performance evaluation of multi-layered coated (TiN/TiCN/TiN) cermet (golden colour) inserts in the dry-hard turning of AISI 4340 steel. The performance of the coated cermet insert was rarely investigated in hard turning. However, it is quite interesting to know its machining capability of the harder workpiece in terms of surface roughness (Ra), the material removal rate (MRR) and chip reduction coefficient (CC). In entire set of L9 experiments, Ra was found to be in the range of 0.212 to 1.452 µm, i.e. within 1.6 µm (standard criteria), hence it justifies that the coated cermet tool can be implemented in hard turning applications to get good quality of finish. Input-terms influence on machining attributes is studied with the help of main effect plot, contour plot, surface plot, and ANOVA. Depth of cut is the supreme input terms to influence the MRR and CC by a contribution of 90.53% and 83.14% exclusively, while feed and depth of cut both are influencing Ra significantly with the contribution of 55.03% and 44.09% correspondingly. Correlation models are formulated using regression theory and found to be satisfactory at 0.05 of the level of significance.