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采用复合电镀技术,通过向普通电镀溶液中分别加入平均粒度为40 nm和1~5μm的Cr粉的方法在Ni基材上制备了一种金属Ni基纳米Cr粒子弥散的Ni-Cr纳米复合镀层和一种微米Cr粒子弥散的Ni-Cr复合镀层。混合盐(75 wt%Na2SO4+25wt%NaCl)750℃热腐蚀行为结果表明:与微米Cr粒子弥散的Ni-12.4 wt%Cr复合镀层相比,Ni-11wt%Cr纳米复合镀层表现出更好的耐腐蚀性能。SEM/EDAX、XRD和TEM分析表明,在相同的Cr颗粒含量条件下,Cr颗粒尺寸的降低提高了Ni-Cr复合镀层的抗腐蚀性能,这是因为Cr颗粒尺寸的降低和基体Ni晶粒的细化增加了单位面积内的Cr2O3形核率,缩短不同Cr2O3核间的距离,与此同时基体Ni晶粒的细化有利于保护性氧化物形成元素Cr沿晶界向腐蚀前沿的快速扩散,从而加速了保护性Cr2O3膜的快速形成。
A composite Ni-Cr nano-composite coating with Ni-based nano-Cr particles dispersed on a Ni substrate was prepared by a composite electroplating technique by adding Cr powder with an average particle size of 40 nm and a thickness of 1-5 μm respectively to a common electroplating solution And a micron Cr particles dispersed Ni-Cr composite coating. The results show that the Ni-11wt% Cr nano-composite coating shows a better corrosion resistance than the Ni-12.4wt% Cr composite coating with micron Cr particles dispersed at 750 ℃ for the mixed salt (75wt% Na2SO4 + 25wt% NaCl) Corrosion resistance. The results of SEM / EDAX, XRD and TEM show that the reduction of Cr particle size increases the corrosion resistance of Ni-Cr composite coating under the same content of Cr particles because of the decrease of Cr particle size and the decrease of Ni grain size The refinement increased the nucleation rate of Cr2O3 per unit area and shortened the distance between different Cr2O3 nuclei. At the same time, the grain refinement of the matrix was conducive to the rapid diffusion of Cr, a protective oxide forming element, along the grain boundaries towards the corrosion front. Thus accelerating the rapid formation of protective Cr2O3 film.