Predictive models for flank wear on coated inserts

The purpose of this paper is to develop predictive models for flank wear that explicitly incorporate cutting temperature and the physical properties of coatings and work materials. The development of such models can minimizes time-consuming machining experiments in predicting tool life by establishing flank wear models that can be applied to wide classes of coated inserts and work materials. To develop such models, a set of experiments was performed to understand the effect on flank wear due the morphology and amount of the second phase in work materials. The plain carbon steels of AlSl designation 1018, 1045, 1065, 1070, and 1095 in hot-roled (pearlitic) and/or spherodized conditions were turned. The inserts with a single coating of TiN, TiCN, or Al2O3 were used in the cutting experiments. The temperature history at a remote location on the rake face was measured during cutting by using an infrared pyrometer with a fiber optic attachment. This temperature information was used to estimate the steady-state tool-chip interface temperature using the inverse estimation scheme by Yen and Wright (1986). The results were then used to predict the work-tool interface temperature using the scheme suggested by Oxley (1989). The results of this experiment showed that, for the spherodized steels, flank wear per sliding distance (the flank wear rate) increased with the cementite content. For the hot-roled (pearlitic) steels, no conclusive evidence was found that correlates the flank wear rate with the cementite content. However, for pearlitic steels the wear rates, in general, were shown to increase with the flank temperature while for spherodized steels the rates decrease with the flank temperature. The reason for these trends can be explained by the microstructural difference between pearlitic and spherodized steels; therefore, the semi-empirical models of two-body and three-body wear developed by Rabonowicz (1967) and Rabinowicz et al. (1972) can be applied to describe the flank wear process.