Study On Laser Surface Alloying With Niobium On Uranium And Corrosion Resistance Of Processing Layer

Five p rocessing 1 ayer w ith d ifferent n iobium c onsistency h ave b een p repared b y 1 aser surface alloying with niobium plating on depleted uranium. The composition, microstructure, phase structure and distribution of niobium element in processing layer were analyzed, the corrosion resistance capability of processing layer was tested, and the cause of improving of corrosion resistance capability was analyzed.Because of the fast heating and fast cooling in the course of laser surface alloying, crystal grain is too late to grow up well, and crystal grain dimension-was very small, to 0.1 micron. It is primarily pillar crystal, isometric and dendrite in molten zone, and there are few air holes in the bottle of molten pool.After laser melting processing, U-Nb alloy with higher niobium consistency (usually, more than 6wt%) will form metastable gamma phase (for example, LA-1, LA-2 andLA-3 samples), however, U-Nb alloy with lower niobium consistency (usually, less than 6wt%) will form supersaturated a' martensite (such as LA-4 and LA-5 samples).During the course of laser surface alloying, because of the convection in laser molten pool, the distribution of niobium element in processing layer is relatively well-proportioned as a whole, however, there is niobium consistency grad along the deepness direction. By means of adjusting of processing parameter, it can make niobium's distribution more even.The results of corrosion test, which performed in 50ug/g potassium chloride aqueous solution, 90 C vapor and 200 C dry air, indicate that proper increase of niobium consistency can effectively improve corrosion resistance. The corrosion resistance is influenced significantly with phase composition in processing layer, the corrosion resistance of gamma phase U-Nb alloy is better than the alpha's, and single phase U-Nb alloy's is better than double phase's .