Corrosion of multilayer ceramic-coated zirlo exposed to high temperature water

Abstract

The corrosion behavior of ceramic coated ZIRLO tubing was evaluated in supercritical water to determine its behavior in high temperature water. The coating architecture consisted of a 4 bilayer TiAlN/TiN coating with Ti bond coat on Zirlo tubes using cathodic arc physical vapor deposition (CA-PVD) technique. On exposure to deaerated supercritical water at 542 °C for 48 h coated tubes exhibited significantly higher weight gain compared to uncoated Zirlo. Examination revealed formation of a uniform ZrO 2 layer beneath the coating and of a thickness similar to that on the uncoated tube inner surface. The defects generated during the coating process acted as preferential paths for diffusion of oxygen resulting in the oxidation of substrate Zirlo. However, there was no delamination of the coating.