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以费氏粒度为4.1μm的WC粉末和CoCl_2·6H_2O、(NH_4)_2C_2O_4·H_2O为原料,将钴粉制备过程与粉末混合过程相结合,一步还原制备WC-Co包裹粉,并以包裹粉为原料成功制备了WC-8%Co(质量分数)超粗硬质合金。借助扫描电镜、X射线衍射仪、化学元素分析仪、力学试验机等分别对WC-Co复合粉末及硬质合金的微观形貌、物相组成和性能进行表征与分析。结果表明,一步还原法制备的WC-Co包裹粉末中,Co为fcc和hcp双相结构,Co相呈树枝状包裹在WC粉末表面。由该包裹粉制备的硬质合金组织结构均匀,综合性能优异,合金平均晶粒尺寸为8.9μm,密度14.63g·cm~(-3),硬度87.6HRA,抗弯强度2438 MPa,断裂韧性20.92 MPa·m~(1/2)。一步还原包裹粉工艺克服了传统湿磨工艺混料过程中WC粒度显著减小的问题,晶粒度可控性好,且工艺流程简单,有潜在的工业应用价值。
WC powder and CoCl_2 · 6H_2O and (NH_4) _2C_2O_4 · H_2O with the particle size of 4.1μm were used as raw materials to prepare the WC-Co wrapping powder by one-step reduction. Raw materials WC-8% Co (mass fraction) ultra-rough carbide was successfully prepared. The microstructure, phase composition and properties of WC-Co composite powders and cemented carbides were characterized by scanning electron microscopy, X-ray diffraction, chemical elemental analysis, mechanical testing machine and so on. The results show that in the WC-Co coated powder prepared by the one-step reduction method, Co is a two-phase structure of fcc and hcp, and the Co phase is dendritically wrapped on the WC powder surface. Carbide prepared by the wrapping powder has the advantages of uniform structure and excellent comprehensive properties. The average grain size of the alloy is 8.9 μm, the density is 14.63 g · cm -3, the hardness is 87.6 HRA, the flexural strength is 2438 MPa and the fracture toughness is 20.92 MPa · m ~ (1/2). The one-step reduction of the wrapped powder process overcomes the problem of significantly reducing the WC grain size in the conventional wet milling process. The controllable grain size is good, and the process flow is simple and has potential industrial application value.