Use of Tacuchi methods and multiple regression analysis for optimal process development of high energy electron beam case hardening of cast iron

The use of Taguchi methods and multiple regression analysis for the development of a melting process using an optimal high energy electron beam (HEEB) melting process to produce high hardness in metals is presented. The HEEB case hardening process was carried out on ductile and flake cast iron. The processing parameters studied included the substrate material matrix, travel speed, accelerating voltage, electrical current, melted width, beam oscillation, and post-heat treatment temperature. In this study, an L18 orthogonal array was introduced for experimental designs and tests. The 'larger the better' criterion for the signal to noise ratios was used as a quality characteristic to evaluate the experimental results. Multiple regression analysis demonstrated better accuracy for forecasting the micro-hardness value of the HEEB melted specimens than the Taguchi methods. The first generated an average error of 3-867% from predicted values, whereas the latter produced an average error of 8-953%. The experimental results suggested that the most significant process parameters were the travel speed, accelerating voltage and post-heat treatment temperature. The largest hardness value obtained through the optimal conditions was 941-67 HV. The microstructures of the specimens were examined and revealed fine primary dendrites and martensite in the HEEB melted layer.