The zirconium alloy cladding is the core component of the reactor in the nuclear power plant. During the service process, the cladding is affected by the axial and transverse flow formed by the high temperature, high pressure, and high-velocity water, which is easy to undergo impact-sliding coupling wear along the axial and radial directions with the positioning grid, resulting in the early failure of the cladding and the leakage of fission products. The work aims to investigate the impact-sliding wear behavior of fuel cladding under different impact energies and the mechanism of pre-oxidation treatment to improve its wear resistance. Firstly, the fuel cladding was pre-oxidized by a special autoclave. Before the wear test, the hardness, surface roughness, and phase composition of the pre-oxidized layer were characterized and tested by a Vickers hardness meter, white light interferometer, and X-ray diffractometer, and the surface morphology and thickness of the oxidative layer were measured through optical microscope, scanning electron microscope, and energy dispersive spectrometer. Finally, the special impact-sliding wear test equipment was used to carry out the impact-sliding wear test on the cladding before and after the pre-oxidation treatment under three different impact energies, to obtain the impact wear rule of the cladding under different impact energies and reveal the mechanism of improving the anti-wear performance of the pre-oxidation treatment technology. A parallel line contact form of tube/plane was adopted in the test and the test parameters were as follows: the sliding velocity was 90 mm/s, the impact velocity was 60, 90, and 120 mm/s, respectively and the number of cycles was 1×104. After the test, a white light interferometer was used to test the wear scars, and the 3D morphologies of wear scars, cross-section profiles, wear area, and wear volume were obtained. The morphologies of wear scars were obtained by optical microscope and scanning electron microscope. After pre-oxidation treatment, the hardness of the cladding was about 233.5HV0.2, which was 22.3% higher than that of the substrate (191.0HV0.2), and the surface roughness was 0.306 μm, which was 33.2% lower than that of the substrate (0.458 μm). The results showed that the impact force, friction, friction coefficient, absorbed energy, and wear volume of the cladding increased with the increase of impact energy whether before or after the pre-oxidation treatment, and the energy absorption rate increased firstly and then decreased. When the impact energy EI was 3.60 mJ, the impact rebound speed, energy, and impact force of the pre-oxidized cladding were slightly higher than that of the substrate. The energy absorption rate, tangential friction force, friction coefficient, and wear volume decreased from 39.1%, 53.9 N, 0.59, and 8.45×105 μm3 to 37.7%, 44.90 N, 0.39, and 8.01×105 μm3, respectively. The pre-oxidation treatment technology was helpful to reduce the wear degree of the cladding. Besides, with the increase of impact energy, the wear mechanism of the uncoated cladding changed from abrasive wear and mild fatigue wear to delamination. The pre-oxidation treatment can effectively increase the rebound speed of the cladding, reduce the friction force, decrease the friction coefficient and energy absorption rate, and finally reduce the wear volume, change the wear mechanism into slight abrasive wear and fatigue wear, and effectively improve the impact-sliding wear resistance.
Key words
fuel rod /
zirconium alloy /
pre-oxidation /
impact-sliding wear /
wear resistance /
wear mechanism
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Funding
National Natural Science Foundation of China (12202465); Sichuan Natural Science Foundation Program (2025ZNSFSC1344); Fundamental Research Funds for the Central Universities (25CAFUC04017)
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