合金元素Ta、Ag对镍基合金机械性能和摩擦学性能的影响及机理研究

利用高能球磨和真空热压烧结方法制备了添加Ta和Ag的镍基复合材料. 考察了复合材料在宽温域范围内的摩擦磨损性能和力学性能，利用SEM、XRD等表征分析其物相组成、磨损机理及断裂机制. 结果表明: 热压烧结过程中，Ta与石墨模具中的C反应生成TaC陶瓷相并在基体中弥散分布；Ta、Ag的加入降低了材料的摩擦磨损，NiCrMoAl-Ta-Ag复合材料实现了在室温~800 ℃的连续润滑，室温时Ag提供润滑作用，中温时由磨屑和Ag形成局部润滑膜，800 ℃时磨损表面形成了含氧化物、钼酸银和Ag的润滑膜. 加入Ta极大提高了材料的机械性能，NiCrMoAl-Ta合金在室温~1 000 ℃具有优异的机械性能，归因于原位生成的TaC和Al₂O₃陶瓷相的弥散强化；材料的断裂机制随温度升高由微孔聚集型断裂转变为以微孔聚集型和氧化断裂为主的断裂. 

Influences and Mechanisms of the Alloying Elements Ta and Ag on the Mechanical and Tribological Properties of Nickel-Base Alloys

Nickel-based composites with addition of Ta and Ag were prepared by high-energy ball milling and vacuum hot-pressing (HP) sintering methods. The tribological and mechanical properties of the composites in a wide temperature range were investigated. The phase composition, wear mechanism and fracture mechanism were analyzed by scanning electron microscopy and X-ray diffraction. During the HP sintering process, Ta reacted with C in the graphite die and formed a TaC ceramic phase which dispersed in the matrix. The addition of Ta and Ag reduced the friction and wear of the material, and the NiCrMoAl-Ta-Ag composite achieved continuous lubrication from room temperature to 800 ℃. Ag provided lubrication at room temperature, and discrete lubricant film was formed by abrasive debris and Ag at intermediate temperature, while at 800 ℃, a continuous lubricant film containing oxide, silver molybdate and Ag was formed on the worn surface. The addition of Ta significantly enhanced the mechanical properties of the material. The NiCrMoAl-Ta alloy had excellent mechanical properties in wide temperature range (room temperature ~ 1 000 ℃), which was attributed to the dispersion strengthening effect of the in-situ generated TaC and Al₂O₃ ceramic phase. The fracture mechanism of the materials varied from micro-void coalescence fractures to the fracture combining micro-void coalescence and oxidative fractures with increasing temperature.