Application of Response Surface Methodology for Modeling of Laser Transformation Hardening of Commercially Pure Titanium ASTM Grade3

Abstract

In the presented study, the laser transformation hardening of commercially pure titanium sheet material of thickness being 1.6mm is investigated using CW, 1.6 kW solid State Nd: YAG laser. A Full Factorial Design (FFD) with Response Surface Methodology (RSM) is employed to establish, optimize and to investigate the relationships of three laser transformation hardening process parameters such as laser power, scanning speed, and focused position on laser hardened bead profile parameters such as hardened bead width, hardened depth, heat input and power density. In this work, Laser Transformation Hardening (LTH) with high precision and an optimum desired minimum value of hardened depth of 241 microns has been accomplished with heat input = 150 J/cm and power density = 294.08 W/mm2 for the laser process parameters of lower beam power: 750 Watts, high scanning speed: 3000 mm/min and a defocused beam of –30 mm. Effects of laser process parameters on laser hardened bead geometries were carried out using RSM. Results indicate that the scanning speed has a positive effect on all hardened bead dimensions while the laser power has a positive effect particularly on hardened bead width as compared to hardened depth and heat input. The optimum laser hardening conditions are identified sequentially to minimise hardened depth, heat input, power density and maximum hardened bead width. The validation results demonstrate that the developed models are accurate with low percentages of error.