Abstract
Metallurgical studies on the bonded interlayers of Ni-base superalloy MM 007 joints were carried out during transient liquid insert metal diffusion bonding (TLIM bonding). The formation and growth mechanism of solid during isothermal solidification process in TLIM bonding was also investigated. Based on these results, the mechanism of TLIM bonding was considered.
Main experimental results obtained in this research are as follows.
(1) Microstructures of the bonded interlayers of joints made at 1423K for 3.84ks were characterized by the insert metals. In the case of Ni-Si-B alloys, MBF-30 and MBF-35, coarse γ' phase were produced in the bonded interlayer. In the case of Ni-Cr-B alloy, MBF-80 and Ni-Co-Si-B alloy, MBF-90, coarse γ' phases were not produced, and fine γ' phases were produced in the bonded interlayer.
(2) In the isothermal solidification process of TLIM bonding, solids grew epitaxially from mating base metal inward the liquid insert metal and grain boundaries were formed at the intersections of growing solids.
(3) The growth mechanism of solid into transient liquid phase in TLIM bonding was equal to that in the fusion welding.
