Cemented carbide tools suffer from many issues due to the use of tungsten and cobalt as raw materials. Indeed, those are listed by the European Commission as “critical raw materials” since 2011 and by the US Department of Interior as “critical minerals” in 2018. To remain competitive with the conventional high-speed steels, less performant but cheaper, WC–Co tools can be recycled. In the present paper, a WC–7.5Co powder, recycled by the “Coldstream” process, has been sintered with vacuum sintering. As preliminary experiments have shown that the sinterability of the powder is low, the sintering temperature was set at 1500 °C to achieve full density. In parallel, the influence of ball milling conditions (rotation speed and milling medium) on the reactivity of the recycled powder has been studied in terms of grain size distribution, hardness, and fracture toughness. The optimized milling conditions were found to be 6 h wet milling, leading to a hardness of about 1870 HV₃₀ and a toughness of about 10.5 MPa√m after densification. The recycled powder can thus totally compete with conventional powders, opening avenues for the recycling of cemented carbide tools.

Graphical Abstract

中文翻译：

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再生WC-Co粉末的加工研究：是否可以与常规WC-Co粉末竞争？

由于使用钨和钴作为原材料，硬质合金刀具遭受许多问题的困扰。实际上，自2011年以来，这些材料已被欧盟委员会列为“关键原料”，而在2018年被美国内政部列为“关键矿物”。为保持与传统高速钢的竞争，性能较差但价格便宜的WC–合作工具可以回收。在本文中，通过“冷流”工艺回收的WC-7.5Co粉末已通过真空烧结进行了烧结。初步实验表明，粉末的可烧结性很低，因此将烧结温度设定在1500°C即可达到全密度。同时，还研究了球磨条件（转速和研磨介质）对再生粉末反应性的影响，包括粒度分布，硬度，和断裂韧性。发现最佳的研磨条件是6个小时的湿研磨，从而产生大约1870 HV的硬度₃₀，致密化后的韧性约为10.5MPa√m。因此，回收的粉末可与传统粉末完全竞争，为硬质合金刀具的回收开辟了道路。

图形概要