Akihiko Ikegaya

Material design method for the functionally graded cemented carbide tool

The aim of this study is to apply the concept of functionally graded materials (FGMs) to tool materials and to develop high-performance cutting tools. The requirement of the graded structure is that the surface is highly wear resistant cermet, and the inside is tough cemented carbide. Compressive residual stress was introduced to the material surface by grading the composition. To develop the new material, the cutting condition of broken cermet was investigated and their cutting temperature distribution was measured by a newly developed measuring method. Then Computer Aided Engineering (CAE) analysis was performed to calculate the generated thermal stress. The new material was developed with the aim to introduce the compressive residual stress over the calculated thermal stress. As a result developed tools demonstrated higher wear resistance, breakage resistance, thermal crack resistance and peeling resistance over those of conventional tools in the market.

Study on the Composition Graded Cemented Carbide/Steel by Spark Plasma Sintering

Abstract: Steel coated with high wear–resistant and high corrosion–resistant hard materials are widely used, but these composite materials do not always achieve the aimed properties, mainly because coating materials with high hardness could not be applied thickly and also could not be jointed firmly as desired. To overcome these problems, the new functionally graded materials were studied. To relieve the thermal stress, Co composition graded cemented carbide powders stacked in multiple layers on steel substrate were sintered and joined on the steel by the Spark Plasma Sintering. Because of low–temperature and short–time sintering, the graded composition of cemented carbide was maintained as desired and a crack– and peel–free coated product could be achieved by this process. From this study, we confirmed that it is possible to realize a high wear–resistant cemented carbide/steel composite material for practical use.

Performance of Tungsten-Based Alloy Tool Developed for Friction Stir Welding of Austenitic Stainless Steel

As the cost-effective tool material, W-based alloys containing hard particles, exhibiting high strength, ductility, and thermal conductivity at high temperatures, were newly developed for FSW of austenitic stainless steel in this study. The W-based alloy tools containing various hard-particles were employed in FSW of type 304 austenitic stainless steel, and the wear behavior was examined. The W-based alloy tools coated by a ceramic exhibited the good performance during FSW, but the tool wear could not be completely prevented. Degree of the tool wear depended on the high-temperature strength, i.e., it decreased with increasing high-temperature strength. The tool wear was significantly suppressed in the W-based alloy with the higher high-temperature strength, and the tool shape was hardly changed even after the 20 m travel on the tool with 1.7 mm long probe.