Structure and Tribological Properties of Surface Carburized Layer on Pure Niobium AITranslate

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Chinese Library Classification Number:TG147[金属学及工艺—金属材料]

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The pure niobium was subjected to surface carburization by vacuum carburizing technology.The microstructure,elemental distribution and phase structure of the carburized layer were characterized by SEM,EDS and XRD.And the bonding strength,hardness and wear resistance of the carburized layer and substrate were evaluated by surface scratches,nano-indentations and friction and wear tests.The results show that the thickness of the carburized layer on pure niobium after carburizing at 1 400 ℃ for 12 h is about 37.8 μm,and the formed carburized layer consists of inner and outer layers.The outer layer is entirely composed of NbC phase while the inner layer contains NbC phase and Nb₂C phase.The carburized layer is dense and uniform without holes and cracks,presenting good bonding performance with the substrate.The hardness and elastic modulus of the pure niobium are greatly improved by carburizing,with the surface nano-hardness increasing from 1.8 GPa to 23.5 GPa.Compared with pure niobium,the friction coefficient of the carburized layer decreases from 1.03 to 0.62 during the friction process with Si₃N₄ friction pair,and the specific wear rate decreases from 21.6×10^-5 mm³/(N·m) to 1.12×10^-5 mm³/(N·m),indicating an improvement of wear resistance.Severe wear is observed on the surface of pure niobium with adhesive and abrasive wear mechanisms,while only slight wear appears on the carburized layer due to the presence of the NbC hard phase with the abrasive wear mechanism.