YG8硬质合金渗硼层组织和性能的分析

用Ｘ射线衍射、电子探针、透射电镜和光学金相方法，研究了钨钴类硬质合金渗硼层的硬化机理。结果表明：ａ）钨钴类硬质合金渗硼导致显微组织发生变化，碳化钨颗粒的间距增大，棱角变圆，相对量减少。ｂ）ＹＧ８渗硼层中发现了钴的硼化物和钨的硼化物，前者的硬度为１４００～２０００ＨＶ；后者的硬度为２０００～３１００ＨＶ．ｃ）电子探针分析表明：渗硼过程中在硼的扩散层内元素重新分布，钴向内迁移，钨和碳向外扩散．ｄ）ＹＧ８硬质合金渗硼层硬度为２７００ＨＶ以上，耐磨性明显提高。渗硼工艺可用于硬质合金高速拉拔模具。

致密碳化硼基陶瓷的强韧化机理研究进展

针对碳化硼陶瓷难烧结、韧性低的缺点,通过引入稀土化合物、SiC、过渡金属硼化物、碳纳米管、石墨烯以及金属相等增强相能够充分发挥碳化硼陶瓷高硬度、高强度的优势,扩大其作为重要结构陶瓷的应用范围。相对而言,SiC与TiB_(2)是目前B_(4)C最有效的增强、增韧相,两者复合添加时,其强韧化机制包括颗粒增韧、固溶强化、热膨胀系数失配导致的裂纹偏转、桥接作用。从不同增强、增韧相与碳化硼间的搭配以及引入方式出发,探讨了碳化硼基陶瓷的强韧化机理与行为,并展望了其多元、多结构体系设计的主要方向。

高熵碳化物/硼化物陶瓷的研究现状及展望

高熵陶瓷通常是指由5种或5种以上陶瓷组元形成的多组元固溶体,具有极高的硬度和模量、较低的热导率及良好的抗氧化性等优良性能,在航空航天、高速切削工具等极端使役环境下展现出巨大的发展潜力。然而,目前高熵陶瓷的研究尚处于起步阶段,理论判据及成分设计理论的完善、固溶耦合机制的建立、制备方法的优化、高通量计算的应用都是未来亟需研究的方向。本文总结和分析了高熵陶瓷的研究现状,主要介绍了高熵碳化物/硼化物陶瓷的体系设计、制备工艺及性能特点,并对其发展方向进行了分析和展望。

Tribological behavior of hot-pressed boron carbide with oxidation

The oxidation behavior at 973 1 273 K and the effect of oxidation on the room temperature tribological properties of hot pressed boron carbide ceramic were investigated. Oxidized samples were studied by X ray diffractometer and scanning electron microscopy. It is demonstrated that the oxidation results in the formation of a thin transparent B 2O 3 film, and the oxide film is severely cracked during cooling due to the thermal expansion mismatch between the oxide film and B 4C substrate. B 2O 3 reacts with moisture in air to form boric acid, which is a kind of solid lubricant. The sliding friction factors of oxidized B 4C pair are about 0.05 0.08, compared to 0.25 0.35 of the as received B 4C pair. When the oxidation temperature is up to 1 273 K, severe unstability and increase of friction factor are observed. Visual inspection of the wear track reveals that the lubricant film is broken and some debris particles occur on and around the rubbing surfaces, because the friction interface is rough by the severe etching of grain boundaries.