Fuel failure caused by fretting damage to cladding remains a relevant issue despite decades of research and development aimed at enhancing the physical parameters of fuel. This paper presents the results of experiments conducted at the Research Centre Řež on Zr-1%Nb alloy tube specimens covered with protective coatings made of chromium (Cr) and nitrogen (N) compounds. The experiments involved debris-fretting tests under dry conditions at room temperature as well as microscopic measurements of groove depths. A detailed analysis was performed using the Scanning Electron Microscopy, Energy-Dispersive X-Ray Spectroscopy, Electron Backscatter Diffraction, and Focused Ion Beam techniques. The objectives of the tests were (1) to compare the debris-fretting resistance between the reference Zr-1%Nb specimens and those of the same alloy coated with various compositions, and (2) to demonstrate the positive effects of coating applications on the endurance of fuel cladding. The conducted analysis revealed a significant advantage in using cladding with a thin, wear-resistant layer compared to standard cladding material, with the CrN-coated specimens exhibiting 36 times better fretting resistance.

Despite decades of advancements and research aimed at improving fuel’s physical properties, fretting damage to fuel cladding remains a significant challenge. This study outlines the findings of experiments conducted on Zr-1%Nb alloy coated with protective layers composed of chromium-aluminium (CrAl) compounds and other new perspective materials, such as FeCrAl and CrNi alloys, at the Research Centre Řež. The experiments included debris-fretting tests performed under LWR conditions (320 °C and 15 MPa) and microscopic evaluations of groove depths. The primary goals were: (1) to evaluate the debris-fretting resistance of uncoated Zr-1%Nb samples compared to Zr-1%Nb with coatings and new alloys, and (2) to investigate the potential effects of coatings and new materials on the durability of fuel cladding. The conducted experiments and studies confirmed the benefits of the wear resistance of the ATF types of claddings in comparison to the standard Zr-1%Nb cladding material. Various parameters, such as wire wear and the influence of mutual position of the samples, were considered during the testing to provide the most precise insight into the wear resistance of the tested samples.