Simulation of Residual Stresses in Cemented Carbide

Sammanfattning: Cemented carbides are used in a multitude of applications within machining as they can withstand tough conditions. Therefore, the stress state in a virgin material is of interest. After cooling from the sintering stage during cemented carbide production, the large difference in coefficients of thermal expansion of the constituents results in thermal residual microstresses. These may be of significant magnitude that could influence the material's performance in later applications. The present work is therefore concerned with these thermal residual microstresses and deals with them through 2D finite element calculations in ANSYS APDL. The geometry was chosen to try to emulate different conditions that could happen within a cemented carbide grain. The tungsten phase was modeled as fully elastic and the cobalt phase as elastic-plastic with linear hardening. The results show that the stress levels reach such magnitudes that the simple material models used in this work, as well as in previous works, are not sufficient to accurately capture the behavior of the material. The stress levels far exceed the strength of the materials, which would cause them to fail. However, that is not the case in reality. Further, the simulations showed that the microgeometry plays a large role in the distribution of the stresses within each phase. In general, the cobalt phase is subjected to tension and the tungsten phase to compression. However, under certain conditions parts of the tungsten phase can also show tensile stresses.