Thermal stability and corrosion resistance in a novel nickle aluminum bronze coating by laser cladding

In this study, the question of whether it is possible to significantly improve the thermal stability and corrosion resistance of a novel nickel aluminum bronze (NAB) coating was investigated. To address this question, a novel NAB coating was firstly prepared on a steel using a semiconductor laser. Microstructure, phase constituents and corrosion resistance of the novel NAB coating with various tempering temperatures were studied with XRD, OM, EDS, SEM and potentiodynamic polarization measurements) in 3.5 wt% NaCl solution (open to air) at ambient temperature (22 degrees C-25 degrees C), respectively. Experiment results exhibited that the cladding layer was mainly composed of alpha-Cu, beta'(AlCu3), Cr-Fe and kappa (Al-Fe-Ni) phase for 400 and 500 degrees C tempering. And beta' disappeared as tempering temperature was up to 600 degrees C, resulting from the occurrence of an eutectoid reaction. With the increase of tempering temperature, Cr-Fe phase became coarse and kappa phase became small, respectively. The corrosion resistance was significantly improved after tempering. The values of i(corr) for all NAB coatings with tempering were one order of magnitude lower than that of NAB coating without tempering. With the increase of tempering temperature, the corrosion potential (E-corr) increased firstly and then decreased gradually. The E-corr of NAB coating with 500 degrees C tempering reached the maximum (-0.21 V), exhibiting the highest corrosion potential and lowest corrosion tendency.