Optimization of Residual Stresses in Hard Turning of Super Alloy Inconel 718

Abstract The residual stresses are the stresses that remain in the component even after the removal of applied force. They may be tensile as well as compressive in nature. The effect of compressive residual stresses on the quality of the machined component as well as its life is less when compared to the tensile residual stresses. In the current study, machining of super alloy Inconel 718 has been done using TiCN – Al 2 O 3 coated cemented carbide tool inserts with the view of optimizing the process parameters in order to minimize the residual stresses. In addition to the residual stresses, surface finish and material removal rate are also optimized in order to improve the machining process.XRD technique has been used in determining the residual stresses induced during machining. Grey relational analysis which is an effective multi objective optimization tool has been applied to experimental results in order to optimize the machining of Inconel 718 with consideration to multiple performance measures. The approach incorporates the use of L9 orthogonal array with grey relational analysis. Grey relational theory is used to evaluate the best process parameters that minimizes the Residual stresses as well as surface roughness, and maximizes the Material Removal rate. The response table and the graph for Grey relational grade for each level of the machining parameters had been plotted. The parameters: cutting speed 52.87 m/min, feed rate 0.20 mm/rev and depth of cut of 0.40 mm have highest grey relational grade and therefore are the optimum parameter values that produces better turning performance in terms of the responses considered for study. Feed rate shows statistical significance on overall turning performance at a confidence interval of 95%.