Diffusion Bonding between Cemented Carbides Using Interlayer

Abstract

Cemented carbides (WC-Co) that consist of tungsten carbides and cobalt have been utilized preferentially for cutting tools. However, since cemented carbides are made of rare metal, establishment of the technology for reuse and recycling are earnestly desired. If cylindrical shanks that the cutting edges are cut off can be combined with each other, it is possible to reuse those shanks as new cutting tools. Till today, joining method generally used for shanks is brazing. But, the joining strength of brazed joints tends to be rather weak for being used as cutting tools.
In our previous study, cemented carbides were successfully joined by the diffusion bonding. The strength of joints by the direct diffusion bonding at bonding temperature 1200°C was almost equal to the strength of base material. However, since there are some cases of using cemented carbides with polycrystalline diamond for bonding, the temperature of 1200°C can be too high.
In this study, on the assumption that the strength of the diffusion bonding was higher than that of the brazing, to lower the bonding temperature, a feasibility for applying the diffusion bonding between cemented carbides using Ni or Co as interlayer was fundamentally verified. The strength of joints with interlayer by the diffusion bonding at the bonding temperature 1100 - 1000°C was stable and equal to the strength of brazed joints. Co interlayer was more effective than Ni interlayer. And the feasibility of the diffusion bonding with interlayer was clarified.