Establishing Empirical Relationships to Predict Grain Size and Hardness of Pulsed Current Microplasma Arc Welded Inconel 625 Sheets

Abstract

Nickel alloys have gathered wide acceptance in the fabrication of components, which require high temperature resistance and corrosion resistance, such as metallic bellows used in expansion joints in aircraft, aerospace and petroleum industry. In case of single pass welding of thinner sections of this alloy, pulsed current microplasma arc welding was found beneficial due to its advantages over the conventional continuous current process. The paper focuses on developing mathematical models to predict grain size and hardness of pulsed current microplasma arc welded Inconel 625 nickel alloy. Four factors, five level, central composite rotatable design matrix is used to optimize a number of experiments. The mathematical models have been developed by response surface method. The adequacy of the models is checked by ANOVA technique. By using the developed mathematical models, grain size and hardness of the joints can be predicted with 99% confidence level. Contour plots are drawn to study the interaction effect of pulsed current microplasma arc welding parameters on fusion zone grain size and hardness of Inconel 625 weld joints.