摘要
由于不同材料的热膨胀系数不同,涂层在冷却过程中可能因为热应力不同而产生裂纹,表面富粘结相的梯度硬质合金基体因粘结相含量高,韧性好,能有效吸收裂纹扩展时的能量,延长涂层刀具的使用寿命。为了研究WC晶粒度对梯度硬质合金的组织及性能的影响,制备了三种WC粒度的硬质合金。采用XRD和SEM对梯度硬质合金的相成分、微观组织进行了分析。实验结果表明,三种WC晶粒度的硬质合金表面均形成了梯度层。随着WC晶粒度的增大,梯度层厚度减小,抗弯强度和断裂韧性增大。三种梯度硬质合金表层显微硬度分布趋势相似。当WC晶粒度较小时,梯度硬质合金无梯度的合金芯部断裂形式均以沿晶断裂方式为主,随着WC晶粒度的增加,穿晶断裂方式增多;梯度表层出现了Co相变形和撕裂形貌,存在蜂窝状的韧性花样。
Cracks will initiate in coating during cooling because the thermal expansion coefficient of coating and substrate is different. The cemented carbide with binder phase enriched gradient surface layer can efte, ctively absorb the energy introduced by crack propagation and prolong the service life of the cutting tools due to its higher binder phase content and better toughness. In order to investigate the effect of WC particle size on the microstructure and properties of the gradient cemented carbide, three kinds of gradient cemented carbide with different WC particle size were prepared. The binder phase composition and microstructure of the gradient cemented carbide were studied by XRD and SEM, respectively. The results show that gradient layers are formed on the surface of all these kinds of cemented carbide. With the increasing of WC grain size, the thickness of the gradient layers decreas, whereas the transverse rupture strength and fracture toughness both increase. The microhardness of the surface on the gradient cemented carbide is similar. The bulk of the gradient cemented carbide is fractured mainly according to intergranular fracture at small WC grain size but transgranular fracture is increased with the increasing of coarse WC grain size. While cobalt deformation, tearing morphology and honeycomb pattern appear in the gradient surface layers.
出处
《硬质合金》
CAS
2015年第6期364-371,共8页
Cemented Carbides
基金
四川省科技计划项目:高性能硬质合金材料与制品制造关键技术研究(2014GZ0086)
关键词
梯度
组织
硬度
断裂形貌
gradient
microstructure
hardness
fracture morphology
