Applying the diffusion bonding theory of green P/M compacts during sintering, the diffusion bonding of green P/M compacts with wrought steel parts is also possible. In general, as the wrought steel parts displayed larger expansion than the P/M green compacts during the heating stage in sintering, in most cases, specimens consists of outer green compacts and inner wrought steel parts yield high bonding strength. However, there are some differences in the diffusion mechanism which results in different bonding strength between three types component - green compacts, sintered compacts and wrought steel components. In the cases of specimens consist of outer Fe green compacts and inner Fe-lC components, the combination of an inner green compact and an outer green compact shows the highest bonding strength, the combination of an inner wrought steel component and an outer green compact shows the second higher strength, and the combination of an inner sintered compact and an outer green compact shows the lowest bonding strength. These are considered to be based on the differences in carbon diffused states and pores distributions on the joining faces before sinter-bonding. The diffusion bonding data on two cases of material combinations are additionally shown. One consists of Fe-0.6P green compact and AISI304L wrought steel shaft which is studied to develop soft magnetic plunger with non-magnetic shaft. The other consists of Fe-Ni-Cu-Mo-Mn-C based green compacts and Cr-Mo steel shafts which was studied to develop cam-shafts for automobiles. In both cases, good diffusion bonding is also obtained.
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