In this paper, gradient cemented carbides with the cubic-phase free in the surface layer were prepared, and the compositional gradient formation was explored. The relations between the properties of the gradient cemented carbide and the TaC addition were investigated. The results showed that the inward Ta migration during the gradient-structure formation of the cemented carbide WC-Co-(W,Ti)C-Ti(C,N)-TaC-W was mainly driven by the thermodynamic coupling between Ta and Ti. The thickness of the cubic-phase free layer decreased as the total Ta/C ratio is enlarged in the gradient cemented carbide. With TaC added in the gradient cemented carbide, the undissolved Ti(C,N) cores was rarely observed in the bulk owing to the solid solution of Ta. The average sizes of WC phases and (W,Ti)C phases could be reduced by the TaC addition, but hardly refined further when TaC exceeds its solubility in the binder. All of the transverse rupture strength, the hardness and the fracture toughness increased with the low TaC content but decreased with the high TaC content. The coercive force was elevated with TaC added in the gradient cemented carbide, and the magnetic saturation increased when increasing TaC contents. Additionally, the coercive force was raised while the magnetic saturation fell down after the cubic-phase free layer was removed.

本文制备了表面层中无立方相的梯度硬质合金，并探讨了成分梯度的形成。研究了梯度硬质合金的性能与TaC添加量之间的关系。结果表明，在硬质合金WC-Co-（W，Ti）C-Ti（C，N）-TaC-W的梯度结构形成过程中，Ta的向内迁移主要是由Ta与Ti之间的热力学耦合驱动的。 。在梯度硬质合金中，随着总Ta / C比的增大，立方相自由层的厚度减小。在梯度硬质合金中添加TaC后，由于Ta的固溶体，很少能在主体中观察到未溶解的Ti（C，N）核。加入TaC可以降低WC相和（W，Ti）C相的平均尺寸，但当TaC超过其在粘合剂中的溶解度时，很难进一步精制。TaC含量低时，所有的横向断裂强度，硬度和断裂韧性均随TaC含量高而下降。在梯度硬质合金中添加TaC可以提高矫顽力，而当TaC含量增加时，磁饱和度会增加。另外，在去除立方相自由层之后，矫顽力增加而磁饱和度降低。随着TaC含量的增加，磁饱和度增加。另外，在去除立方相自由层之后，矫顽力增加而磁饱和度降低。随着TaC含量的增加，磁饱和度增加。另外，在去除立方相自由层之后，矫顽力增加而磁饱和度降低。