WC-Co梯度硬质合金的本构关系及应用

Constitutive equation for WC-Co functionally graded cemented carbides and application

摘要:

功能梯度硬质合金实现了高硬度与高强度的完美结合. 然而, 由于材料成分及物性的梯度变化使得材料内部的残余热应力影响了产品的性能. 为了分析制备及服役过程中梯度硬质合金中残余应力的影响, 通过定义弹性约束因子和引入塑性约束因子得到了材料的弹塑性本构关系. 将此本构模型结合有限元方法得到了梯度硬质合金内部残余热应力的分布. 数值计算结果表明: 残余热应力主要集中在样品近表面的梯度区. 在富钴区出现了拉应力, 而在表明出现了压应力, 表面最大压应力有380MPa. 同时, 采用X射线衍射法测试了样品的表面应力, 得到的结果是-379.75Mpa. 实验观测与数值模型符合较好.

Abstract:

Functionally graded cemented carbides (FGCCs) have an excellent combination of high hardness and high toughness. But the appearance of residual stresses, resulting from cobalt gradient and mismatch between mechanical properties and material constituents, is an influence on the lifetime of FGCCs. To get the thermal stress field distribution, a constitutive equation for WC-Co FGCCs is developed by redefinition of elastic constraint factor and introduction of plastic constraint factor. The constitutive model is applied to thermal stress analysis of WC-Co composites. The distribution of thermal stresses in WC-Co specimen is obtained by means of finite element numerical method. Simultaneously, the surface compressive stress of FGCCs alloy is measured by X-ray diffraction method. Numerical results show the thermal stresses of WC-Co composites mainly concentrate in the cobalt gradient zone and the maximum value of principal compressive stress is 380MPa in the surface zone. This results is good agreement with X-ray diffraction measurement.