Application of Taguchi Approach and Utility Concept in Multi-Objective Optimization of Laser Transformation Hardening of Commercially Pure Titanium for Heat Input and Tensile Strength

摘要

This research article primarily focuses on multiperformance optimization of tensile strength and of laser transformation hardening of commercially pure titanium sheet of ASTM Gr.3 with thickness being 1.6mm Using Taguchi Methodology and Utility Concept using a continuous wave (CW) 2kW, solid-state Nd:YAG laser. Taguchi optimization method for simultaneous minimization of heat input (HI) and tensile strength (σ) is influenced by laser transformation hardening parameters: laser power (LP), scanning speed (SS), and focused position (FP) of laser transformation hardened commercially pure titanium. The effect of these process parameters on the heat input (HI) and tensile strength (σ) properties of commercially pure titanium and subsequent optimal settings of the process parameters have been obtained using Taguchi's parametric design approach and utility concept. The response performance is analyzed based on signal-to-noise ratio and analysis of variance (ANOVA). The optimal levels of the laser process parameters were determined through the Analysis of Means (ANOM). The results demonstrate that the scanning speed (SS) and the laser power (LP) are the significant parameters in deciding the tensile strength and heat input of laser transformation hardened commercially pure titanium. The confirmation tests with optimal levels of laser process parameters were carried out to demonstrate the effectiveness of Taguchi optimization method. The optimization results revealed that a combination of higher levels of scanning speed (SS) and focused position (FP) i.e., increase in defocus along with laser power (LP) in the lower level play important role in order to simultaneously minimize the heat input (HI) and to maximize the tensile strength (σ). The predicted optimal values of tensile strength and heat input of commercially pure titanium sheet produced by laser transformation hardening process are 464 N/mm~2 and 141.667 Watts, respectively, for the optimized laser process parameters with minimum LP=750 Watts, maximum SS=3000mm/min, and lower value of FP=-30mm (increase in defocus).