Multilayer (TiN, TiAlN) ceramic coatings for nuclear fuel cladding

• The first study on multilayer TiAlN and TiN ceramic coatings on ZIRLO® coupons.
• Corrosion tests were performed at 360°C and 18.7 MPa for up to 90 days.
• Coatings adhered well to the substrate, and showed no spallation/delamination.
• Weight gains were six times lower than those of uncoated ZIRLO® samples.
• Longer and higher temperature corrosion tests will be discussed in a further paper.

In an attempt to develop an accident-tolerant fuel (ATF) that can delay the deleterious consequences of loss-of-coolant-accidents (LOCA), multilayer coatings were deposited onto ZIRLO® coupon substrates by cathodic arc physical vapor deposition (CA-PVD). Coatings were composed of alternating TiN (top) and Ti1-xAlxN (2-layer, 4-layer, 8-layer and 16-layer) layers. The minimum TiN top coating thickness and coating architecture were optimized for good corrosion and oxidation resistance. Corrosion tests were performed in static pure water at 360 °C and 18.7 MPa for up to 90 days. The optimized coatings showed no spallation/delamination and had a maximum of 6 mg/dm2 weight gain, which is 6 times smaller than that of a control sample of uncoated ZIRLO® which showed a weight gain of 40.2 mg/dm2. The optimized architecture features a ∼1 μm TiN top layer to prevent boehmite phase formation during corrosion and a TiN/TiAlN 8-layer architecture which provides the best corrosion performance.