Theory of chip formation in grinding of biphasic brittle materials using the example of WC-Co carbide

WC-Co硬质合金的相组成和WC晶粒度分布对硬质合金的硬度H、杨氏模数E和临界断裂韧性KIC等材料性能有显著影响。此外，在第一个研究阶段已经证明，硬质合金的规格对材料的去除行为有很大的影响，从而也影响硬质合金的加工质量。硬质合金的磨削除了要有较高的加工质量外，还必须满足经济性的要求。一个成本驱动因素是磨具磨损。必须假定硬质合金规格对磨具磨损有决定性影响。目前尚不清楚相组成和WC晶粒度分布对磨具磨损的影响。因此，研究项目的目的是描述和解释磨削过程中刀具磨损与WC-Co硬质合金规格之间的关系。为了研究磨损机理，进行了单颗粒切割试验。通过对划痕的分析，可以定量研究磨粒的磨损情况。通过扫描电子显微镜和透射电子显微镜对磨粒进行定性分析，还可以确定磨损机制。然后进行磨削试验，以检查砂轮磨损，并检查单颗粒切割试验结果的可转移性。最后，建立了WC-Co硬质合金磨削过程中刀具磨损的定性描述和解释模型。

The phase fractions and the WC grain size distribution of WC-Co cemented carbides significantly influence their material properties such as, the hardness H, the Youngs modulus E and the critical fracture toughness KIc. Furthermore, during the first research period it was proven that the cemented carbide specification significantly influences the material removal behavior and consequently also the quality of the workpieces of the cemented carbides. In addition to high workpiece quality, grinding of cemented carbides has to meet economical requirements as well. A cost driver is the grinding tool wear. It must be assumed that the cemented carbide specification has a decisive influence on the grinding tool wear. Currently it is unknown how the phase fractions and the WC grain size distribution affects the grinding tool wear. Therefore, the aim of the research project is a description and an explanation model for the tool wear as a function of the WC-Co cemented carbide specification in grinding. For the investigation of the wear mechanisms, single grain cutting tests are carried out. By an analysis of the scratch tracks, the quantitative wear of the grains can be investigated. The qualitative analysis of the grains by means of scanning electron and transmission electron microscopy additionally enables the identification of the wear mechanisms. Grinding tests are then carried out in order to examine the grinding wheel wear and to check the transferability of the findings from the single grain cutting tests. Finally, a qualitative description and explanation model for grinding tool wear in grinding of WC-Co carbides is developed.