Preparation of UNx by laser nitriding and its corrosion performance

The corrosion resistance of uranium has always been an important issue in the wide use of uranium materials. Surface nitriding has been proved to be one of the best surface anti-corrosion modification methods. In the present study, the nitrided layer with different nitrogen content was prepared on the surface of uranium by laser nitriding technique. The surface morphology and lattice structure were characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The electronic structures and oxidation behaviors were analyzed by X-ray photoelectron spectroscopy (XPS). Corrosion resistance was analyzed by electrochemical test. The results show that the main phase in the nitrided layer is UN and metal uranium. The nitrogen always exists in the oxidized state of the nitrided layer. The nitrogen element in the crystal lattice may enhance the oxidation resistance of uranium surface. The electronic structure and valence band structure of UNx films with different nitrogen content and their depth-dependent information were obtained. Excessive nitrogen content will lead to the initiation of microscopic cracks, which destroy the integrity of nitrided layer and reduce the corrosion resistance in solution. UN0.35 nitrided layer is well matched with lattice of the base metal, and the surface is intact without cracks, showing the best solution corrosion resistance.