| Zirconium alloys were laser surface melted (LSM) using a continuous wave CO{dollar}sb2{dollar} laser at energy densities of 4, 7, and 10 kJ/cm{dollar}sp2{dollar}. Melt widths were overlapped by 50% to achieve complete coverage. Laser melted pool depths and hardness profiles were a function of the applied laser energy densities. LSM samples examined using SEM and optical microscopy exhibited ultrafine martensitic microstructures. LSM samples were examined for alloy segregation using TEM electron diffraction, SEM-EDX, and SIMS. Corrosion performance was obtained by three techniques: (1) steam autoclave tests (400{dollar}spcirc{dollar}C, 1500 psig), (2) immersion tests in 10% FeCl{dollar}sb3{dollar} at room temperature, and (3) potentiodynamic tests in 10% FeCl{dollar}sb3{dollar} at room temperature. Potentiodynamic results were in agreement with immersion results. Coarser microstructures performed better than fine microstructures in autoclave tests, while fine microstructures performed better than coarse microstructures in 10% FeCl{dollar}sb3{dollar} tests. LSM samples showed a 600-fold improvement in performance over wrought material when tested in 10% FeCl{dollar}sb3{dollar}. Accelerated corrosion (nodular corrosion on coupons tested in autoclave and pitting corrosion on coupons tested in 10% FeCl{dollar}sb3{dollar}) occurred near the laser beam overlap region. Sn and Fe alloy elements segregated near the periphery of each melt pool. Segregated regions containing increased Fe concentrations associated with each laser pass were responsible for accelerated corrosion. |
