High Pressure Sintering of Super-hard Boron Suboxide and Evaluation of Sintered Compacts

氧化六硼（b_60）是一种超硬硼化合物，其显微硬度可与金刚石或立方氮化硼相媲美，有望实际应用于切削工具或喷嘴部件。然而，B_60很难烧结和致密化，其机械或热性能迄今为止鲜为人知。本文以实验室合成的可烧结B_60粉末为原料，通过高压高温处理，制备了高密度B_60烧结坯。然后，我们研究了烧结后的压块的力学和热性能，并评估了应用于各种工具的可能性。B_60粉体的合成与表征将无定形B_20_3与硼（物质比为1:16）的混合物在纯氩气流中加热（1350℃，4 h）合成B_60粉体。通过扫描电镜观察，合成的B_60粉末由直径为1.2 ~ 1.4 μ m的晶体和分散性颗粒组成。2 .更多。B_60粉末的高压烧结及其烧结坯的力学性能和热性能采用环式高压装置研究了真空处理B_60粉末的最佳烧结条件。在5 GPa、1700℃、20 min的高温高压条件下，制备了单相b_60烧结体。相对密度为97%，维氏显微硬度为3400 kg/mm^2。TG-DTA分析表明，B_60烧结坯具有比B4C更高的抗氧化性，并且在1000℃以下发生了轻度氧化，同时形成了液态B_2O_33保护层。为提高B_60烧结致密体的韧性，研究了B_60基烧结复合材料的制备及其在B_60- b_4c体系或B_60- cbn体系中应用于刀具复合材料的可能性。对真空处理后的B_60和B_4C/cBN混合粉末在3 ~ 8 GPa、150 ~ 1800℃、15 ~ 30 min条件下进行高压和高温处理。两种体系的显微硬度和断裂韧性最大值分别为4600 kg/mm^2和1-1.8MNm^<-3/2>。少

Hexaboron oxide (B_6O) is one of the super-hard boron compounds which has a microhardness comparable to diamond or cubic boron nitride, and is expected to an actual application to cutting tools or nozzle parts. However, B_60 is so difficult to sinter and to densify the compact that its mechanical or thermal property is less known so far. In the present paper, we prepared B_60 sintered compact in full density by high pressure and high temperature treatment of sinterable B_60 powder which was synthesized in our laboratory. Then, we investigated the mechanical and thermal properties of the sintered compacts and evaluated the possibility of application to various tools.1.Synthesis and characterization of B_60 powderB_60 powder was synthesized by heat treatment (1350ﾟC, 4 h) of the mixture of amorphous B_20_3 and boron (1 : 16 in mol ratio) in an pure argon stream. The synthesized B_60 powder was observed by SEM to comprise crystalline and dispersible particles with 1.2-1.4 mu m diameters.2 … More .High pressure sintering of B_6O powder and the mechanical or thermal properties of the sintered compactAn optimum sintering condition of the vacuum treated B_60 powder was investigated using the girdle-type high pressure apparatus. A single phase B_6O sintered compact was prepared by the high pressure and temperature treatment at 5 GPa, 1700ﾟC and 20 min. The relative density and Vickers microhardness were 97% and 3400 kg/mm^2, respectively. TG-DTA analyses exhibited that B_60 sintered compact had an oxidation resistance higher than B4C, and a mild oxidation proceeded up to 1000ﾟC accompanied by a formation of protective layer of liquid B_2O_33.Preparation of B_60-based sintered composites and their possibility for application to toolsSintered composites in the B_60-B_4C system or B_60-cBN system were prepared in order to increase the toughness of B_60 sintered compact. High pressure and temperature treatments of the vacuum treated mixed powder of B_60 and B_4C/cBN were carried out under the conditions of 3-8 GPa, 150O-1800ﾟC and 15-30 min. Maximum values of microhardness and fracture toughness in both systems were 4600 kg/mm^2 and 1-1.8MNm^<-3/2>, respectively. Less