Deposition of amorphous SiC coatings by RF sputtering and properties optimization for multifunctional barrier applications in the breeding blanket of nuclear fusion reactors

Abstract

The development of multifunctional coatings that simultaneously prevent Tritium (T) leaks and Li corrosion of the structural steel is necessary to ensure safe operation of breeding blankets (BBs) that use liquid metals, such as the Water-Cooled Lithium Lead (WCLL) design in nuclear fusion reactors. In this work, we present the development of amorphous Silicon Carbide (a-SiC) coatings deposited by Radio-Frequency (RF) magnetron sputtering as a potential candidate for this application. We characterize the morphology, elemental composition, density, microstructure, hardness and adhesion to the substrate of the coatings as a function of deposition parameters (Ar mass flow rate and bias voltage) and of the bonding material. We observe that low Ar mass flow rates (40 sccm), low bias voltages (-30 V) and Cr bonding lead to amorphous coatings with homogeneous and compact morphology, a high density of 3.15 g/cm³, and quite good adhesion (critical load of 303 mN) to the steel substrate for the aimed purpose. The studied coatings also present a hardness of 30 GPa and a reduced elastic modulus of 246 GPa. Such combination of properties makes a-SiC coatings a promising candidate to act as a multifunctional barrier in the breeding blanket of nuclear fusion reactors operating both in the inertial and magnetic confinement approaches.