Evaluation of thermal shock strength of thermal-sprayed coatings by the laser irradiation technique

Abstract

Ceramic coatings by thermal spraying have excellent wear- and heat-resistant characteristics. Therefore, it is very important to investigate their thermal shock resistance. This paper presents a novel method for evaluating thermal shock resistance of ceramic coatings by laser irradiation technique. The critical power density of a laser beam is introduced to measure a fracture criterion, which corresponds to a critical temperature difference for bulk ceramics. Using this, critical fracture curves are obtained experimentally, which are a function of the coating thickness and beam diameter. These critical fracture curves are also obtained theoretically based on a simple numerical model. Both the results show a reasonably good agreement. It was concluded that the thermal shock strength of thermal-sprayed coatings decreases with increasing coating thickness.