A Study of the Interface Layers of a Double Nano /Micro Layer Zirconia Coating

The Generation IV gas-cooled fast reactor (GFR) nuclear system features a fast-neutron-spectrum and helium-cooled reactor. The helium coolant operates at 7 MPa with an outlet temperature of 850.C and the challenging issues for the GFR design involve the development of in-core and out-of-core materials capable to resist to fast-neutron damage and high temperatures in accident situations.

This work deals with a double-layer plasma-sprayed zirconia coating for the protection of out-of-core metal alloy structures to depressurization events. The coating system consists of a thin nanostructure layer and a thick microstructure layer. The first layer deposited by suspension plasma spraying provides the adhesion of the coating on the smooth and thin (1-mm thick) metal substrate while the top layer, deposited by conventional plasma spraying, acts as a thermal barrier. The interface zones are investigated by various techniques to better understand the adhesion mechanisms between the various layers of the system.