PACK CEMENTATION ON T91 STEEL : FRACTURE SURFACE ANALYSES TO UNDERSTAND THE MECHANICAL BEHAVIOUR AT 300°C IN CONTACT WITH LEAD-BISMUTH LIQUID METAL

摘要

Different coatings, deposited by pack cementation process, were developed to protect the T91 steel towards the dissolution by Lead Bismuth Eutectic (LBE): iron aluminide, iron boride and an iron solid solution enriched in chromium and covered by a chromium carbide. The mechanical behaviour of the T91 with the different coatings is studied in air and in LBE at 300°C by the use of the Small Punch Test (SPT). In SPT, specimens in the form of disk are punched in their middle by a ball. The fracture surfaces of the T91 steel and of the coatings are observed after test by scanning electron microscopy. The fracture of the interface between the steel and the coating appears as a key factor to understand the mechanical behaviour of the coated T91 steel in contact with the Lead-Bismuth Eutectic.