预处理工艺对放电等离子烧结超细晶WC-Co硬质合金组织和性能的影响

Effect of Pretreatment on Microstructure and Properties of Ultrafine WC-Co Cermets by Spark Plasma Sintering

采用不同粒度的WC粉与超细Co粉混合得到初始粉末,利用直接放电等离子烧结(SPS)技术和一种包括真空预处理和SPS烧结的新制备方法,研制超细晶WC-Co硬质合金块体。结果表明,两种不同粒度匹配的混合粉末经真空预处理后SPS烧结得到的试样较直接SPS烧结试样的硬度稍有降低,但断裂韧性得到提高,尤其是抗拉强度得到显著提高。对试样显微组织和性能分析表明,混合粉末的真空预处理工艺对SPS烧结WC-Co硬质合金具有重要作用:去除混合粉末吸附气体,消除Co池,同时保证WC晶粒不发生明显长大。

WC powders with different particle sizes and ultrafine Co powders were mixed to form the initial powders.Afterwards ultrafine WC-Co cermet bulks were prepared by direct SPS and a new method combining vacuum pretreatment with SPS.Results show that the samples prepared by pretreatment and SPS have a little lower hardness but higher fracture toughness and much higher tensile strength than those by direct SPS.The analyses of microstructures and properties indicate that the vacuum pretreatment has important effect on the WC-Co cermets by SPS.It can release the adsorbed gas,cancel the ＂Co lake＂ and obtain completely densified bulks without significant grain growth.