铬颗粒尺寸对镍-铬复合镀层900℃抗空气氧化和耐Na_2SO_4熔盐腐蚀性能的影响

Effect of Cr Particle Size on the Oxidation in Air and Hot-corrosion Resistance in Molten Na_2SO_4 Salt of Ni-Cr Composite Coatings at 900 ℃

采用复合电镀技术,在镍基体上分别制备了纳米铬-镍复合镀层和微米铬-镍复合镀层,用XRD、SEM/EDS等仪器分别对两种复合镀层在900℃空气中的氧化行为和在900℃Na2SO4熔盐中的热腐蚀行为进行了研究。结果表明:与微米铬粒子增强的Ni-30%Cr复合镀层相比,纳米铬粒子增强的Ni-11%Cr复合镀层表现出更好的抗高温氧化和耐腐蚀性能;铬颗粒尺寸的减小增加了单位面积内Cr2O3的形核量,缩短了不同Cr2O3核间的距离,从而加速了保护性Cr2O3氧化膜的快速形成,这是Ni-11%Cr复合镀层抗氧化和耐腐蚀性能更好的主要原因。

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-ll~ 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.