Corrosion behavior of Cr coating on ferritic/martensitic steels in liquid lead-bismuth eutectic at 600 °C and 700 °C

Abstract

The surface coating technology, encompassing ceramics, refractory materials, metallic alloys containing Al or Si, and multicomponent composites, presents a viable approach to improve the corrosion resistance of ferritic/martensitic (F/M) steels with (9–12) wt.% Cr in liquid lead-bismuth eutectic (LBE) environment. Among these coating materials, chromium (Cr) coating emerges as a particularly noteworthy option. This study specifically focused on depositing a 3 μm thick Cr coating on on T91 and SIMP steels using magnetron sputtering. Subsequently, the corrosion behavior of the Cr coating was investigated in LBE at temperatures of 600 °C and 700 °C. The results revealed that, after 300 h at 600 °C, T91 and SIMP steels formed oxide scales with approximately 32.6 μm and 19.3 μm thicknesses, respectively. At 700 °C for 140 h, these oxide scales increased to about 82.4 μm and 73.1 μm for T91 and SIMP steels, respectively. However, the application of a Cr coating resulted in the formation of a dense layer of chromium oxide with a thickness of 4–5 μm. This layer effectively impeded oxygen diffusion and Fe migration leading to a significant reduction in the corrosion rate of the steel. Notably, the Cr coating maintained secure attachment to the steel even after exposure to high-temperature LBE corrosion. These findings underscore the capacity of coating to markedly enhance the corrosion resistance of T91 and SIMP steels in high-temperature LBE environments, providing robust protection against the detrimental effects of challenging conditions. Consequently, Cr coating emerges as a promising solution for future fission nuclear reactors.

Keywords

• Cr coating
• Magnetron sputtering
• LBE corrosion
• Oxide scale
• Effective barrier