Coatings on Steels T91 and 316L in Lead-Bismuth Eutectic Environment

Abstract

The work is aimed on the coatings used as a barrier against Heavy Liquid Metal (HLM) influence and coated material behaviour under mechanical loading. The comparison of two kinds of coatings deposited on two different steels is examined: ferritic-martensitic steel T91 coated with AlTiN and austenitic steel 316L coated with Al 2 O 3 . Both samples underwent tensile tests with constant extension rate in the HLM autoclave-cell for material testing. The testing environment in the cell was liquid PbBi eutectic at the temperature of 550 °C. The examination by Scanning electron microscopy and Energy-dispersive X-ray spectroscopy followed after exposure. The yield strength of the steel was exceeded in both cases, cracks and adhesion were studied in depth to characterize their resistance to the simultaneous effect of load and environment. Both coatings offered protection against corrosion; however, localized cracking gave rise to the damage of the substrate. These coatings provided a corrosion barrier, which once damaged is not able of self-healing.