Laser Processing of Thermal Sprayed Coatings for Thermoelectric Generators

Abstract

Recent research has shown that thermal spray has the potential to fabricate thermoelectric devices at low cost and high volumes. An integral aspect of the device fabrication is laser processing of the various thermal sprayed layers, which is used to form electrically isolated regions and minimize heat loss to adjacent structures. In this article, experimental results are presented for the laser patterning of thermal spray samples ranging from 50μm to 2mm in thickness. The optimization of process parameters is important for successful electrical isolation and high-quality features. In this study results are presented several short-pulse lasers (nanosecond and picosecond) in which laser power, laser wavelength, type of focusing lens, processing speed, repetition rate, and pressure and flow of purge gas were varied. The optimum laser parameters were those that minimize the heat affected zone and delamination due to thermal damage while providing maximum material removal. The resulting laser patterns were characterized using both optical and scanning electron (SEM) microscopy, and by verifying electrical isolation between patterned regions using contact resistance measurements. Cut quality attributes including kerf width and edge profile were also studied, and their dependence on process parameters reported.