Effect of laser surface melting on the corrosion and cavitation erosion behaviors of a manganese-nickel-aluminium bronze

Manganese-nickel-aluminium bronze (MAB) samples were treated with a high-power Nd:YAG laser system to achieve laser surface melting. Under proper laser processing conditions, the cavitation erosion-corrosion rate of laser-treated MAB in 3.5 wt.% NaCl solution was reduced by more than five times compared with that of as-received MAB. To elucidate the mechanism leading to enhancement in resistance, pure corrosion in 3.5 wt.% NaCl solution and pure cavitation erosion behaviors were studied separately. Pure corrosion behavior was studied using electrochemical technique and immersion method under quiescent condition, while pure cavitation erosion behavior was studied using deionized water as a non-corrosive medium. Both the corrosion resistance and the erosion resistance benefited from a homogeneous single-phase microstructure resulting from laser surface melting, while the relatively low resistance of as-received MAB was mainly attributable to its heterogeneous and multi-phase microstructure. The increase in erosion resistance was more significant than that in corrosion resistance, probably due to the increase in hardness as an additional favorable factor for erosion resistance. For laser-treated MAB, erosion-corrosion synergism constituted a significant contribution to the overall cavitation erosion-corrosion in 3.5 wt.% NaCl solution. The shift in corrosion potential under cavitation revealed the difference in the relative dominance of the effect of cavitation on the cathodic and anodic reactions on laser-treated and untreated MAB samples. (C) 2004 Elsevier B.V. All rights reserved.