Stability of plasma-sprayed TiN and ZrN coatings on graphite for application to uranium-melting crucibles for pyroprocessing

摘要

The high-temperature stability of ZrN and TiN coatings deposited by plasma spraying on graphite crucibles for melting uranium was investigated. A layer of mixed Zr (or Ti) oxide and nitride was formed with a thickness of 80-100 mu m. The chemical stability was evaluated by a melting test with uranium at 1400 A degrees C. The ZrN layer disappeared after the melting test, but the TiN layer remained stable. The thermal stability was evaluated by heating up to 1400 A degrees C; the surface of the crucible coated with ZrN flaked off after this test, whereas the surface of the crucible coated with TiN remained almost intact.