Bonding of W and Mo Plates to Fe and Ni Substrates Using HIP

Abstract

Plates (M₁) of tungsten and molybdenum with 0.3 and 0.2mm thick have been bonded to substrates (M₂) of iron and nickel, respectively, under HIP at 800-1200°C, 10-200MPa for 30min. Because the HIP method results in complete contact at the M₁-M₂ interface, no pores were observed. A diffusion layer was observed between M₁, and M₂, and its thickness, including the reaction layer, increased with an increase in temperature. Thickness decreased with an increase in HIP pressure, suggesting that the pressure suppresses the diffusion of the atoms of M₁ and M₂. Despite the large difference in the thermal expansion coefficients of M₁ and M₂, the bonding resisted over 40 repetitions of 900°C thermal shock. It is suggested that the diffusion layer act to reduce thermal stress. Further, since the interface did not give even under bending stress, it is suggested the HIP pressure plays an important role in increasing the strength of the bond between M₁ and M₂.