采用大气等离子喷涂、爆炸喷涂和超音速火焰喷涂三种热喷涂技术制备了NiCr/Cr_3C_2-BaF_2·CaF_2涂层,分析比较了涂层的显微组织、物相组成、孔隙率、硬度、结合强度及其摩擦学性能.结果表明,与大气等离子喷涂相比,超音速火焰喷涂和爆炸喷涂技术制备的涂层具有更高的致密度、硬度和结合强度.采用包覆法制备的粉末进行喷涂,碳化物失碳明显减少,涂层中氧化物含量低.三种NiCr/Cr_3C_2-BaF_2·CaF_2热喷涂涂层的摩擦系数都随着温度的升高而减小,爆炸喷涂和超音速火焰喷涂涂层的摩擦系数比等离子喷涂涂层的摩擦系数更低,耐磨性得到提高.高温下BaF2·CaF2润滑膜的形成均可有效降低三种涂层的摩擦系数,从而降低涂层和对磨球Si3N4的磨损率.
Microstructures, composition, porosity, hardness, bonding strength and tribological properties of NiCr/Cr_3C_2-BaF_2·CaF_2 coatings prepared with plasma spraying (APS), detonation spraying (DS) and high velocity oxy-fuel spraying (HVOF) was systematically investigated. The results show that using coated spray powders, the decarburization of carbide, oxidation and ablation are reduced in thermal spray process. The NiCr/Cr_3C_2-BaF_2·CaF_2 coatings deposited by HVOF and detonation spraying have higher density, hardness and bond strength with comparison to plasma spraying. The friction coefficients of three kinds of NiCr/Cr_3C_2-BaF_2·CaF_2 coatings decrease with the increasing temperatures, and the high temperature friction coefficients are significantly lower than that at room temperature. The friction coefficients of HVOF and detonation spraying coatings are lower than plasma spraying coating, and HVOF and detonation spraying coatings show better wear-resistance. The friction coefficients and wear rates of three coatings as well as the wear rates of coupled Si3N4 balls are reduced due to the formation of BaF2·CaF2 lubrication layer at elevated temperatures.
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