The present work investigates the effect and optimization of process parameters on the cutting temperature, tool wear and metal removal rate during hard milling of 100MnCrW4 (AISI O1) tool steel using (TiN/TiAlN) coated carbide tools. The central composite rotatable design is utilized to plan the experiments. The empirical models were developed and analysis of variance tests were used for the investigation of significant parameters and adequacy of models. Scars, adhered materials and coating peel off were observed on the rake face of the tool due to the existence tool flank wear through the SEM and EDX analysis. In order to seek optimal parameters, a Non-dominated Sorting Genetic Algorithm (NSGA-II) has been adopted and a set of Pareto-optimal solution set was obtained. Further, a set of confirmation experiments were conducted and the adopted optimization method was proved to be feasible. Also, the results would be more useful to guide the actual hard milling process parameters for predicting the responses.Keywords Hard milling, Central composite rotatable design, Cutting temperature, Tool wear, Metal removal rate, NSGA-II.
INTRODUCTIONHard milling is a viable green machining technique, which is more alternative to replace the grinding process at the semi-finish stage and also replacing the EDM process (Ding T et al., 2010 andDavim JP, 2011). The technology offers for significant savings in cost, good surface finish with large metal removal rate as compared with EDM (Gopalsamy BM et al., 2010). A successful implementation of hard milling describes that to boost the productivity with improved surface quality. On the other hand, it generates more fluctuated cutting forces and temperature as compared with conventional machining process. This causes severe tool wear in the cutting tool, then reduces the tool life and deteriorates machining quality. The tool wear is associated with cutting temperature and metal removal rate, being three important responses in hard milling to designate the required surface finish. Therefore, the influence of hard milling process parameters is still questionable to predict the quantitatively the technological performance of machining operations at economic level. Ding T et al. (2010) studied the effect of cutting speed, feed rate and depth of cut on the cutting forces, and surface roughness in hard milling of AISI H13 (50±1 HRC) steel with coated (TiN/TiAlN) carbide tool. Siller HR et al. (2009) demonstrated the special tool geometric features of coated carbide tools in face milling of hardened D3 tool steel (60HRC) components of dies and molds. The surface roughness was revealed in the range between 0.1-0.3 µm with an acceptable level of tool life. Zhang S et al. (2012) carried out experimental investigations on hard milling of AISI H13 (50±1HRC) tool steel to determine the effects of surface texture, cutting parameters, phase transformation and in-depth residual stress distributions on the surface. It has been concluded that the surface texture of machined surface highly cor...