Characteristic evaluation of HIP bonded SS/DSCu joints for surface roughness

Bonding technologies of SS/DSCu, SS/SS and DSCu/DSCu using HIP method have been developed for the fabrication of the ITER shielding blanket first wall. In this study, the effect of the roughness of the HIP bonding surface has been studied for the 1–40 μm roughness from the view points of bondability of surfaces by HIPping and simplification of fabrication procedure. For the tensile properties, it has been found that the effect of the roughness within above range is negligibly small. On the other hand, it has been confirmed that the finer the surface roughness, the higher impact properties for the DSCu/DSCu joints. Significant differences are not found in the SS316L/DSCu and SS316L/SS316L joints with 1–40 μm, though the finer the surface roughness, the slightly higher the impact energy value. Also, it has been found that the HIP bonded joint with good bondability is obtained by using higher HIP pressure, i.e. 200 MPa even with coarser surface roughness, i.e. ∼10 μm, to reduce the machining requirement in the fabrication procedure. In the fabrication of the International Thermo-nuclear Experimental Reactor (ITER) shielding blanket, conditions of the surface roughness and the Hot Isostatic Pressing (HIP) pressure will be selected by taking into account the machining cost for surface preparation and the HIP process cost based on dimensions of the part to be HIP bonded.