Effect of Cr Particle Size on the Oxidation in Air and Hot-corrosion Resistance in Molten Na₂SO₄ Salt of Ni-Cr Composite Coatings at 900℃

Nanoparticle-dispersed Ni-Cr composite coatings and microparticle-dispersed Ni-Cr composite coatings were developed by composite electroplating of Ni with Cr nanoparticles and Cr microparticles on nickel base metal,respectively.The oxidation in air and hot-corrosion behavior in molten Na2SO4 salt at 900 ℃ of the codeposited Cr nanoparticles dispersed Ni-11% Cr composite coating and Cr microparticles dispersed Ni-11% Cr composite coating was studied using SEM/EDS and XRD.The results show that Ni-11%Cr composite coatings exhibited superior oxidation and corrosion resistance compared to Ni-30%Cr composite coatings.The reduction of Cr particle size significantly improved the oxidation and hot corrosion performance of the codeposited Ni-Cr composite coatings.This is attributed to an increase of the nucleation sites on the surface for Cr2O3 formation and simultaneously a promotion of lateral-oxide growth.