Wear Partition of PWR Control Rod Cladding Under Impact–Sliding Loading

This study investigates the wear behavior of PWR control rod cladding under three representative loading modes: pure impact, circumferential sliding, and impact–sliding coupling, in high-temperature (300 °C) and high-pressure (15.5 MPa) water. Pre-oxidized and non-oxidized specimens were compared using white-light interferometry, net mass change, SEM, and EDS. Maximum wear depth and wear volume were used as the primary quantitative indicators of wear because net mass change may also reflect oxidation, transferred material, and retained debris. The results show that pre-oxidation does not uniformly reduce wear but changes its distribution between the contacting bodies. Under circumferential sliding, for example, pre-oxidation increased the cladding wear depth from 12.85 to 20.05 μm while reducing the guide-card depth from 24.99 to 11.93 μm. Impact–sliding coupling produced a distinct edge-localized wear morphology, although it did not yield the largest value for every wear metric. Surface observations revealed oxide-layer cracking and spallation in pre-oxidized specimens and stronger adhesion-related transfer features in non-oxidized specimens. The results show that control-rod wear assessment should consider not only the total wear magnitude but also its distribution between the cladding and guide card.