Product Code: ICA10_1701

A Thermo-Kinetic Phase Transformation Model for Multi-Pass Laser Heat Treatment by using High Power Direct Diode Laser
Authors:
Soundarapandian Santhanakrishnan, Research Center for Advanced Manufacturing, Southern Methodist University; Dallas TX USA
Fanrong Kong, Research Center for Advanced Manufacturing, Southern Methodist University; Dallas TX USA
Radovan Kovacevic, Research Center for Advanced Manufacturing, Southern Methodist University; Dallas TX USA
Presented at ICALEO 2010

Nowadays, high-power direct diode laser (HPDDL) is successfully used in industry as a versatile tool for locally heat treating the metallic components. Laser phase transformation hardening (LPTH) based on rapid heating and cooling cycles produces hard and wear-resistant layers only at the selective region exposed to the laser heat source. However, a tempered zone is formed in overlapped regions of a large heat treated area during multi-pass laser heat treatment. This study is focused on the development of a uniform hardness distribution model to minimize the tempering effect during multi-pass laser heat treatment. A tool steel AISI S7 is heat treated by using different levels of laser power (1400 W- 1800 W) with different scanning speeds (15 mm/s- 25 mm/s). An experimentally based finite element (FE) model is developed to predict the cross-sectional as well surface temperature field of multi-pass laser heat treatment. The temperature-dependent material properties and phase change kinetics are taken into account in the model. The laser beam is considered as a moving rectangular-shaped heat source (12 mm - 1 mm) with a uniform distribution of laser power. The acquired temperature field from FE model is coupled with thermo-kinetic equations to obtain the corresponding phase transformations and hardness. The effect of multi-pass laser heat treatment on the formation of tempered martensite is studied for different overlapped configurations (1mm - 3 mm). The thermo-kinetic model results are validated with the experimental results to optimize the processing parameters. The optimized processing parameters, including laser power, scanning speed, and overlapping ratio are used to achieve a uniform hardness distribution and an even depth of heat treatment in the multiple-pass laser heat treated area.