Evaluation of adhesion strength of Er₂O₃ coating layer for an advanced breeding blanket system applied to thermal cycles using nano-scratch method

The electrical insulator and hydrogen permeation barrier coatings are important materials to realize the liquid metal and molten-salt typed breeding blanket systems. We found that erbium oxide (Er2O3) is one of the promising materials as the electrical insulator and hydrogen permeation restraint coatings. Establishing the mechanical property evaluation method for these coating is extremely important to certify the durability of coating material in the blanket systems. The adhesion strength property, which is one of the key mechanical properties of coating materials, was investigated using the nano-scratch method. From the results, it was found that the nano-scratch test was able to evaluate the adhesion strength of the Er₂O₃ coating synthesized by the Metal Organic Chemical Vapor Deposition (MOCVD) process with high reproducibility. Furthermore, the adhesion strength of the Er₂O₃ coating before and after thermal cycling was evaluated using this method. The adhesion strength after 50 thermal cycles at 700°C was kept around 70% compared with that before thermal cycling.