电冶熔铸WC/钢复合材料组织及碳化物演变的研究

Microstructure and Carbides Evolution of WC/Steel Matrix Composites by Electroslag Melting Casting

采用电冶熔铸法制备了以GCr15轴承钢为基体,WC颗粒为硬质相的WC/钢基复合材料。借助金相分析、扫描电镜、X射线衍射、透射电镜及能谱分析等方法研究了该材料熔铸态显微组织结构及其演变过程。结果表明:随着加入WC含量和颗粒尺寸的不同,其凝固后组织结构不同。当加入10%WC时,WC颗粒大多溶解于钢液中,冷却后沿晶界析出断续网状复式碳化物,同时基体中析出细小的Cr7C3、β-WC1-x、Fe3W3C颗粒;当加入20%WC时,大颗粒WC外围部分溶解形成Fe3W3C反应层,钢基体中析出共晶碳化物;当加入35%WC时,显微组织主要是以γ-Fe+WC、γ-Fe+Fe3W3C共晶组织为主,多数呈树枝状和锚状,少数为不规则块状;当加入40%或50%WC时,WC颗粒基本保留原始形状且稳定不易溶解,多数呈三角状、矩形,均匀分布。

The WC/steel matrix composites were prepared by electroslag melting and casting Microstructures and evolution of the composites were investigated using optical microscopy, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and Energy dispersive spectroscopy （EDS） as well as transmission electron microscopy. The experimental results show that the solidified microstructure is different with different content and different sizes of WC. When 10% WC is added, most of WC particulates are dissolved into molten steel; the discontinuous netlike compound carbides （Fe3W3C） were precipitated along the grain boundary; Meanwhile, fine Cr7C3, β-WC1-x and Fe3W3C are precipitated in the matrix. When 20% WC is added, the margin of large particulates is dissolved to form Fe3W3C reaction layer, eutectic carbides precipitate in the steel matrix. When 35 % WC is added, the microstructure are mainly consisted of γ-Fe＋WC and x-γ-Fe＋Fe3W3C. most of them is dendritic and anchor-like structure, few has irregular structure. When 40% WC or 50%WC is added, WC particulates almost keep their original shape and they are stable and difficult to be dissolved, and they distribute uniformly and most of them are triangle and rectangle.