Yoshiyuki Nakajima1, Hiroki Esaki2, Masaaki Tobioka3 and Masaharu Tokizane4
1Graduate School of Science and Engineering, Ritsumeikan University, Kyoto. Present address: Sumitomo Electric Industries, LTD., Itami
Diffusion bonding between hard metal (WC-Co) and tool steel (SK5) was carried out by holding at 1103 K for 3.6 ks under the applied pressure of 12 MPa in vacuum using Ni-foil as an insert metal. After such an operation, the specimens were subjected to the further heating at 1273 K (holding for various durations without loading pressure) in order to attain the advanced diffusion.
The experimental results showed that both the decrease of the heating and cooling velocities during the bonding operation and the occurrence of martensitic transformation in the SK5 side of the bonded specimens quenched after heating at 1063 K introduce the reduction of internal stress in the inserted Ni-foil layer. These effects was a cause for an appreciable improvement of the bonding strength.
A high value of bonding strength, 630 MPa, was obtained by the tensile test of the bonded specimens.
diffusion bonding, hard metal, carbon tool steel, insert nickel-foil, martensitic transformation, microstructure, bonding strength
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