基于钴、碳迁移动力的梯度硬质合金制备与材料特性研究

Study on Preparation and Material Characteristics of Gradient Cemented Carbide Based on Driving Force of Cobalt and Carbon

功能梯度硬质合金(FG WC-Co)与WC-Co相比能够提供优异的硬度和断裂韧性组合。基于液相Co从高Co含量向低Co含量、从高C含量向低C含量迁移的钴、碳迁移动力,本文设计了富碳高钴的WC-15%Co和贫碳低钴的WC-6%Co双层样品。采用扫描电镜(SEM)、X射线衍射(XRD)等分析手段,研究了双层硬质合金的微观结构与力学性能。结果表明双层样品中Co相从富碳高钴层向贫碳低钴层迁移形成梯度结构,并且两层间C含量差别越小,Co浓度梯度越大;高钴层中WC晶粒尺寸比低钴层的大,并且两层间C含量差别越小,WC晶粒尺寸差别越大;随着两层间C含量差别减小,矫顽磁力(Hc)减小,钴磁(Com)增加;硬度从1 260 HV至1 408 HV逐渐升高,从WC-15%Co面加压测的抗弯强度2 612 MPa高于从WC-6%Co面加压测的抗弯强度2 388 MPa。

Compared with WC-Co,functionally graded cemented carbide(FG WC-Co) can provide excellent combination of hardness and fracture toughness.Based on the driving force of cobalt and carbon that liquid-Co migrates from higher Co content to lower one,from higher C content to lower one,bilayered samples of WC-15%Co with carbon-rich and high-cobalt layer and WC-6%Co with carbon-depleted low-cobalt layer were designed.The microstructure and mechanical properties of the bilayered cemented carbide were studied by means of scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results show that the Co phase in the bilayered samples migrates from a carbon-rich and high-cobalt layer to a carbon-depleted and low-cobalt layer to form a gradient structure,in addition,as the difference in C content between the two layers decreases,the gradient of Co concentration becomes larger;the WC grain size in the high cobalt layer is larger than that in the low cobalt layer,besides,as the difference in C content between the two layers decreases,the difference in WC grain size becomes larger;as the difference in C content between the two layers decreases,the magnetic coercivity(He)becomes smaller and the cobalt magnetic(Com) becomes larger;the hardness gradually increases from 1 260 HV to1 408 HV,the TRS of 2 612 MPa measured from WC-15%Co is higher than that of 2 388 MPa measured from WC-6%Co.