残余应力对陶瓷/硬质合金复合片硬度的影响

Effect of Residual Stresses on the Hardness of Ceramic/Cemented Carbide Compacts

分析了残余剪应力对材料硬度的影响，导出了残余剪应力与硬度压头下最大剪应力的关系式．分析表明，残余剪应力与残余正应力不同，无论其方向如何，总是使材料硬度下降．通过实验证明，陶瓷／硬质合金热压复合片界面附近，残余剪应力使硬度下降的值大于由于残余压应力使硬度升高的值．据此分析认为，当陶瓷层热膨胀系数比硬质合金层小，而且太薄时，虽然可以在陶瓷层形成较大的残余压应力，但因残余剪应力的影响，表层的硬度不仅不会升高，反而会降低．

The effect of residual sheax stress on the hardness of materials was considered and the relationship between the residual shear stress and the maximum shear strss induced by hardnesspressure head was also deduced. The analysis indicates that the residual shear stress reduces thehardness of materials whatever its direction which is different from the residual normal stress. Thedecease value of hardness by residual shear stress is larger than the increase value of hardness bycompressive stress near the interface of the ceramic/cemented carbide compact. According to this,it is considered that the hardness of the ceramic surface not only can't increase but also decrasedue to the effect of the residual shear stress, although larger residual compressive stress cajn beformed in the ceramic when the ceramic is too thin and its thermal expansion coefficient is smallerthan that of the cemented carbide.