Exposure of pre-stressed T91 coated with TiN, CrN and DLC to Pb–55.5Bi

The aim of this work is the examination of different coatings in order to select the most suitable one for the use in lead bismuth eutectic (LBE) to protect a structural material. The three coatings we have focused on are: TiN + 2–3%Cr (CVD), CrN + W (PVD) and DLC (diamond like carbon; prepared by a developed low temperature process). Coated T91 specimens were exposed to flowing LBE at 350 °C and a static stress (0, 70, 150 and 200 MPa) in the CORRWETT loop. After 1000, 3000 and 6000 h of exposure the specimens were dismounted. Cross section cuts were made of the exposed specimens without removing the adherent solidified melt. Subsequently metallurgical examination, SEM and EDX analyses were carried out. Additionally the surfaces of the cleaned specimens were inspected by SEM and EDX analyses. All investigated coatings showed excellent results concerning their compatibility in LBE. The static stress influenced the stability of CrN and DLC coated specimens but not the TiN coated ones.