Optimization of size and form characteristics using multi-objective grey analysis in abrasive water jet drilling of Inconel 617

Inconel 617, a group D category of Superalloys, is the prime material for ultra-supercritical power plant components. Nontraditional machining methods are explored for machining Inconel 617 as the traditional processes are limited. Abrasive water jet machining is very promising in processing hard-to-machine materials and machining of superalloys using abrasive water jet machining needs attention. This paper focuses on establishing hole characteristics in abrasive water jet drilling using multi-objective grey analysis. The form and orientation characteristics of the hole are defined using entry and exit hole overcut, entry and exit hole circularity, taper angle of hole and depth averaged radial overcut apart from drill rate and surface roughness. The process parameters are water jet pressure, standoff distance, and abrasive mass flow rate. Analysis of variance of the individual responses is used to identify the pattern in which each parameter affects the performance of the process. Interaction effects of the various factors have been elaborated using plots. Analysis of means was conducted to obtain the mean effects plot. The results from analysis of variance and analysis of means were compared and good correlation was obtained. The parameter levels for obtaining optimal individual responses were identified and reported. Grey relational analysis combines the attributes of each of the responses into a single grey grade. The grey grade represents the overall hole characteristic of the drilled hole. Analysis of means of the grey grade gives the optimal parameter setting. The adjudged optimal parameters are tested experimentally and reported.