纯相低氧纳米WC-Co复合粉的制备

Preparation of nano WC-Co composite powders with pure phases and low oxygen content

摘要:

以紫钨、四氧化三钴、炭黑为原料,在高真空度条件下利用原位反应合成技术制备出物相纯净、粒径约为80nm的WC-Co复合粉。研究了制备工艺参数对纳米复合粉相组成、粒径、氧含量及最终烧结硬质合金块体材料组织性能的影响。结果表明,纳米复合粉中氧含量较高时,会导致后续烧结过程中发生脱碳反应,使烧结制备的块体材料致密度和力学性能明显下降。将纳米复合粉在800_oC下真空热处理2.5h可有效降低粉末中的氧含量,同时热处理后的粉末颗粒无明显长大,平均粒径为85nm。向复合粉中加入1.1%TiC与0.9%VC进行SPS烧结,烧结块体平均晶粒尺寸为105nm,且尺寸分布均匀,致密度达99%以上,硬度为2145HV₃₀,断裂韧性达到9.81MPa*m_1/2。

Abstract:

Using tungsten oxide, cobalt oxide and carbon black as the raw materials. The nano WC-Co composite powders with pure phases was synthesized by in-situ reduction and carburization reactions. The particle size of prepared WC-Co composite powders is about 80 nm. In this work, the effects of preparation conditions on the phase formation, particle size and oxygen content of the composite powders and on the microstructure and mechanical property of the sintered bulk were investigated. The results indicate that the decarburization reaction will happen in the process of sintering when the oxygen content of the composite powders is higher, leading to a decrease in density and mechanical property of the sintered bulk. The oxygen content declines significantly, with heat treated for two and a half hours, under the heat treatment temperature of 800 _oC. Meanwhile, the mean particle size with heat-treated is 85 nm, without markedly increase. Using heat-treated composite powders with the addition of 1.1%TiC and 0.9%VC grain growth inhibitors, the nano-grained WC-Co bulk by SPS was obtained, with an average grain size of 105nm. The hardness values and fracture toughness obtained are 2145Hv30 and 9.81MPam_1/2 , superior to unheated sample.