碳化铬/Ni3Al复合堆焊层组织及摩擦磨损分析

采用光学显微镜、扫描电镜、电子探针及X射线衍射分析钨极氩弧堆焊碳化铬增强Ni3Al基复合堆焊层的组织结构,并采用销盘式干摩擦磨损试验机对堆焊层与活塞环用蠕墨铸铁材料的干摩擦磨损性能进行试验比较.结果表明,复合堆焊层内形成Ni3Al金属间化合物基体,其中弥散分布有大量细小的块状和条状碳化物硬质相Cr3C2和Cr7C3;焊接时焊丝中Cr3C2颗粒溶解析出,重新析出的碳化铬颗粒中包含Fe和Ni元素,碳化铬颗粒与Ni3Al基体形成良好的冶金结合;弥散分布的碳化铬颗粒和Ni3Al基体固溶强化的Cr元素决定了堆焊层具有较高的硬度.室温条件下,复合堆焊层具有优异的耐干摩擦磨损性能,其摩擦系数为0.23,远低于活塞环蠕墨铸铁的0.39;磨损率仅为蠕墨铸铁材料的43%.

Analysis on microstructure and friction wear performance of chromium carbide/Ni3Al composite surfacing layer

Microstructure of chromium carbide reinforced Ni3Al-based matrix composite coating prepared by argon tungsten-arc welding was investigated with optical microscope,scanning electron microscopy(SEM),electron probe micro-analysis(EPMA) and X-ray diffraction(XRD).The wear performance of the coating and cast iron of piston ring were tested by a Pin-on-Disc tribometer.The results indicated that the Ni3Al-based matrix was formed during welding,a large number of fine carbide particles such as Cr3C2 and Cr7C3 dispersed in it;The particle of Cr3C2 in welding wire was dissolved and re-precipitated during hardfacing.The re-precipitation of chromium carbide particle contains Fe,Ni elements and forms strong metallurgically bond with Ni3Al-based matrix.Diffuse distribution of chromium carbide particles and Cr solid-solution in Ni3Al-based matrix,makes the surfacing layer with higher hardness.The hardfaceing layer shows excellent dry friction wear resistance and its friction coefficient is 0.23,lower than 0.39 which is the friction coefficient of piston material of vermicular graphite cast iron.The wear rate of hardfaceing layer is only 43 percent of vermicular graphite cast iron.