Dissimilar metal diffusion joining between low thermal expansion alloy

Wakui, Takashi  ; Ishii, Hideaki*; Naoe, Takashi   ; Suzuki, Hiroshi  ; Harjo, S.   ; Futakawa, Masatoshi  

In the diffused bonding by HIP of invar alloy with a low-thermal expansion coefficient and common metal, large residual stresses occurs near the bonding line due to difference with a big thermal expansion coefficient and then we are anxious about the strength reduction by the residual stresses. In this study, some tests for bonding specimen were carried out. The diffusion layer with thickness of 50 micro meter occurred near the bonding line. The neutron diffraction method could not measure the residual stress. In tensile tests, all fractures occurred in invar alloy side and the bonding strength was higher than the strength of Invar alloy. The grain size increased with an increase of treatment temperature and the tensile strength decreased with an increase of the grain size.