Abstract
A functionally graded material is a compound of two different materials with gradient composition. In addition to combining the characteristics of the two materials, this new material is intended to have distinct characteristics of its own that will allow new applications. This concept was applied to the field of hard materials. The developed material consists of a titanium based ceramic surface layer, a tough cemented carbide core containing carbonitride with 131 type and WC phases, and an intermediate layer with graded composition. The surface region is characterized by a high compressive residual stress of 0.8 GPa. In this material development, we investigated the cutting condition under which tools are easily damaged, and used a newly developed temperature distribution measurement method to identify the temperatures generated within the tool under those condition. We used the resulting temperature distribution data to perform CAE analysis in order to calculate the thermal stress generated by temperature distribution change. We confirmed the compressive residual stress of the developed material exceeds the calculated thermal stress. Compared to conventional cermet tools, the developed material tools improved thermal crack resistance, wear resistance and breakage resistance. Furthermore, its wear resistance and peeling resistance are superior to those of coated cemented carbides.
