采用放电等离子(spark plasma sintering,简称SPS)烧结制备出了无粘结相硬质合金材料,并结合XRD、SEM、金相显微镜等分析测试手段,研究了原料粉末中碳、氧含量对无粘结相硬质合金的微观组织和性能的影响.结果表明,原料粉末中游离碳含量过高会造成烧结体晶粒的显著长大,氧含量较高会降低烧结体的致密度,从而导致烧结体的性能变差;采用纯度较高的原始粉末时,维氏硬度达到2566kg·f/mm~2,断裂韧性为6.2MPa/m~(1/2).另外,在500℃对原料粉末进行氢气预处理可以明显降低氧含量,在1700℃下可制备出相对密度达98.8%,维氏硬度为2731kg·f/mm~2,断裂韧性为6.16MPa/m~(1/2)的无粘结相硬质合金材料.
Bulk binderless ultrafine pure WC was obtained by the spark plasma sintering process(SPS).The phase ,microstructure and fracture surfaces of the binderless WC were studied by using X-ray diffraction analysis(XRD),optical microscopy and scanning electron microscopy(SEM).The experiment results show that,when free carbon of the initial power was too high,abnormal grain growth occurred;when the content of oxygen of the initial power was too high,the density of sintered decreased badly.The binderless WC sintered at 1700℃ for 120s showed almost full densification and exhibited excellent mechanical properties when using the best power,the Vickers hardness and fracture toughness obtained were 2566kg·f/mm~2 and 6.2MPa/m~(1/2).In addition,it was found that the content of oxygen could be reduced obviously when the initial WC power was pretreated in H2 atmosphere at 500℃.Then,the binderless tungsten carbide was prepared at 1700℃.The density,vickers hardness and fracture toughness of alloys is 98.8%,2731kg·f/mm~2 and 6.16MPa/m~(1/2) respectively.
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