Changes in adhesion of CrN coatings on Zr-1% Nb alloy substrates preliminary irradiated with high-intense pulsed ion beams

Abstract

Attempts are currently being made to use coatings, including nitride ceramics, for improving func-tional properties of nuclear fuel claddings made of zirconium alloys. However, the incompatibility of material characteristics at the metal/ceramic interfaces, residual stresses in the coatings, as well as the morphology (roughness) of the substrate surface layers cause their low adhesion. As a result, delamina-tion often occurs during operation. This issue can be solved by optimizing the deposition parameters and preliminary treatment of the substrate surfaces by various methods. The authors report changes in adhesion of CrN coatings deposited by reactive magnetron sputtering on substrates from the Zr– 1%Nb alloy, pre-irradiated with a high-intensity pulsed ion beam (HIPIB). The effect of the HIPIB energy density on the morphology, phase composition, microhardness, and free surface energy levels of the modified layers is shown. Finally, changes in adhesion, assessed by scratch tests combined with acoustic emission signal processing, are presented. The results show that the crack initiation threshold decreases by 20% at low energy densities of up to 1 J/cm2, while it increases by 25% at 2 J/cm2.