电沉积Co-Ni-Al2O3复合镀层微观结构及高温性能

在氨基磺酸盐电解液中,利用复合电沉积技术制备得到了Co-Ni合金基中弥散分布Al₂O₃颗粒的金属基复合镀层。通过SEM,AFM以及XRD等分析测试方法,研究了Co-Ni-Al₂O₃复合镀层的表面形貌和微观晶体结构。结果发现:Co-Ni-Al₂O₃的表面形貌和微观晶体结构主要受镀层中钴含量的影响。高钴含量复合镀层具有Hcp结构,其表面形貌比具有Fcc结构的低钴含量镀层的表面更加均匀细致。Al₂O₃颗粒在Co-Ni合金中的共沉积,没有改变合金固溶体的相组成,但却改变了各晶面的优势生长。通过研究复合镀层的硬度、高温耐磨性、高温抗氧化性、热膨胀系数和热导率表明:Co-Ni-Al₂O₃具有较好的高温耐磨性和高温抗氧化能力,并且高钴含量的复合镀层相对于低钴镀层具有较低的热膨胀系数和较高的热导率。 

MICROSTRUCTURE AND PROPERTIES OF Co-Ni-Al2O3 COMPOSITE COATINGS AT THE HIGH TEMPERATURE

The metal matrix composite coating that Al_2O_3 particles incorporate into Co-Ni alloy was prepared by the electrodeposition technique from sulfamate electrolyte. It illustrates from the examined results of SEM, AFM and XRD that surface morphology and microstructure of Co-Ni-Al_2O_3 coatings appear to be mainly influenced by variations in cobalt content. The codeposition of Al_2O_3 particles in Co-Ni alloys cannot change the phase structure of solid solution, only affects the growth and orientation of crystal planes and mostly increases the d value of lattice. The high-temperature properties of the Co-Ni-Al_2O_3 coatings, including hardness, wear resistance, oxidation resistance, coefficients of thermal expansion and thermal conductivity at high temperature were also investigated. The results show that Co-Ni-Al_2O_3 composite coatings have good performance of wear resistance and oxidation resistance at the high temperature. Furthermore, the composite coatings with high-cobalt content show lower coefficients of thermal expansion and higher thermal conductivity than coatings with low-cobalt content do.