| metallugical studies on the bonded interlayer of directionally solidified Ni base superalloy MM-007 joints were carried out during transient liquid phase diffusion bonding(TLP bonding). The formation mechanism cf solid during solidification process in TLP bonding was also investigated. Microstructures of the bonded interlayer of joints made at 1423K for 3.84ks were charaterized by insert metals. In the case of Ni-Si-B alloy, MBF-30, coarse γ′phases were produced in the bonded interlayer. In the case of Ni-Cr-B alloy, MBF-80, coarse γ′ pases were not produced and fine γ′ phases were produced in the bonded interlayer. In the isothermal solidification process, solids grew epitaxially from mating base metal inward the liquid insert metal ;and grain boundaries were formed at intersections of growing solid. It is clarified that directionally solidified alloy can be bonded ideally without. detriment to hardening mecahnism of base metal. Formation of fine grains in the bonded interlayer is due to epitaxial growth from recrystallized grains which formed by machining. In the result of tensile test at 1033K, all joints were fractured at base metal. TLP bonding process can obtain exellent joints. |
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