The Morphologies and Adhesion of Ceramic Films on CLAM Steel Substrates for Nuclear Fusion Applications

In the dual-function lithium-lead test blanket module (DFLL-TBM) thin and durable coatings with a large tritium permeation reduction factor (PRF) and high resistivity are usually used to segregate the structural wall from the liquid Li-Pb. Al₂O₃, Cr₂O₃, SiC, Er₂O₃, et al. are considered as the promising functional coating materials for DFLL-TBM. Due to the thermal expansion coefficients and lattice constants of ceramic and metal materials are quite different, the mechanical properties of ceramic coatings on metal substrates can be reduced by poor adhesion. In this study, Al₂O₃, Cr₂O₃, SiC, Er₂O₃ films were fabricated on China low activation martensitic (CLAM) steel substrates by magnetron sputtering. Atomic force microscope (AFM) was used to study the surface morphologies of ceramic films. The adhesion strength of the films, deposited on CLAM steel, was also studied by scratch test. Results indicate that the surface of SiC films is smoother than the others. While the surface morphologies of Al₂O₃, Cr₂O₃, Er₂O₃ films are similar. The critical load of SiC film, with a minimum value, is about 12.0 mN, while the critical load of Al₂O₃ reaches about 16.4 mN.