Pulsed Laser Treatment of Cr-Coated Zr Alloy for Accident Tolerant Fuel Claddings: Microstructure and High-Temperature Oxidation Behavior

This work investigates the effects of pulsed laser treatment and pre-heating (300 °C and 500 °C) on the microstructure, defect formation, and high-temperature oxidation resistance of a ~15 µm-thick Cr coating on Zr alloy. Studies addressing the combined effects of nanosecond laser processing and substrate pre-heating on the microstructure and high-temperature oxidation behavior of Cr-coated Zr alloys remain limited. This work therefore focuses on clarifying these interrelated effects within the investigated processing range. With increasing energy input, a sequential evolution occurs: from surface cracking, through partial melting with surface oxidation, to extensive intermixing with formation of Cr-Zr oxide phases. Pre-heating of the Cr-coated alloy to 500 °C significantly suppresses thermal-stress-induced coating cracking during laser treatment. The laser-treated Cr coating at optimized parameters exhibits superior protective performance compared to the untreated coating under oxidation in air at 1200 °C. The weight gain of the laser-treated Cr-coated alloy is reduced by more than one order of magnitude relative to the uncoated alloy. These results demonstrate that optimized nanosecond laser treatment with substrate pre-heating is a viable strategy for enhancing the high-temperature oxidation resistance of Cr-coated Zr claddings for accident tolerant fuel (ATF) applications.