Effect of N2 Flow on Microstructure and Properties of CrNx Film Prepared by Unbalanced Magnetron Sputtering on the Surface of Depleted Uranium

The chemical nature of depleted uranium is very active and susceptible to oxidation in nature environment. CrNx films were prepared by unbalanced magnetron sputtering ion plating at different N-2 flow on the surface of depleted uranium to improve its corrosion resistance. The surface morphology, phase structure, chemical state and corrosion behavior of CrNx films were characterized by SEM, XRD, XPS, and polarization curves (Ell). The results show that, phase structure of CrNx film prepared at 10 Sccm N-2 flow is composed primarily of the bcc alpha-Cr. With the increasing of N-2 flow, the phase structures transform to HCP-Cr2N and fcc CrN, which preferred orientation transforms from Cr(110) to Cr2N(111) and CrN(200). When N-2 flow increases from 10 sccm to 50 sccm, the Cr2p3/2 XPS peaks move toward high binding energy side, the content of metal Cr decreases and the content of nitride chromium increases. When N-2 flow increases to 30 sccm, CrNx film has fine grain and better density, its corrosion potential increases to 550 mV and corrosion current density decreases two orders of magnitude. After deposited CrNx film by unbalanced magnetron sputtering, the corrosion resistance of depleted uranium is effectively improved.