The flaking phenomenon often appearing in Al₂O₃-TiC ceramics tools in turning of alloyed tool steels was studied, as a continuation of the previous reports. The Al₂O₃-TiC ceramics having 10-50 mass%TiC and different grain size of TiC were prepared by hot-pressing, and the ceramics tools were subjected to turning tests of SKD11 (ASTM, HB).
It was confirmed that the tools with lower or higher TiC content and with coarser TiC grains showed generally low resistance to flaking. It was found that the flaking originated from a micro-crack formed on the pre-honing surface. The formation of the micro-crack was considered as follows. In the case of the tools with lower TiC content, the amount of flank wear was apt to increase, leading to the increase in the resultant cutting force which sheared the crater surface. On the other hand, in the case of tools with higher TiC content, the amount of adhesion on the pre-honing surface, that is, the amount of the surface wear (crater wear) became larger since the reaction between work and tools during tests was enhanced, resulting in the generation of tensile stress on the pre-honing surface in the course of removing off of adhesion.