Cold spray deposition of Ti2AlC coatings for improved nuclear fuel cladding

Coatings of Ti2AlC MAX phase compound have been successfully deposited on Zircaloy-4 (Zry-4) test flats, with the goal of enhancing the accident tolerance of LWR fuel cladding. Low temperature powder spray process, also known as cold spray, has been used to deposit coatings ∼90 μm in thickness using powder particles of <20 μm. X-ray diffraction analysis showed the phase-content of the deposited coatings to be identical to the powders indicating that no phase transformation or oxidation had occurred during the coating deposition process. The coating exhibited a high hardness of about 800 HK and pin-on-disk wear tests using abrasive ruby ball counter-surface showed the wear resistance of the coating to be significantly superior to the Zry-4 substrate. Scratch tests revealed the coatings to be well-adhered to the Zry-4 substrate. Such mechanical integrity is required for claddings from the standpoint of fretting wear resistance and resisting wear handling and insertion. Air oxidation tests at 700 °C and simulated LOCA tests at 1005 °C in steam environment showed the coatings to be significantly more oxidation resistant compared to Zry-4 suggesting that such coatings can potentially provide accident tolerance to nuclear fuel cladding.