1997 Volume 15 Issue 2 Pages 321-329
The effects of base metal grain size on base metal dissolution and isothermal solidification of Ni-base superalloy, CMSX-2 were investigated employing MBF-80 insert metal. TLP-bonding of single crystal, coarse-grained and fine-grained CMSX-2 was carried out at 1373 K-1523 K for various holding times in vacuum. The dissolution phenomena of base metal were followed by Nernst-Brunner's theory in any base metal grain sizes. The saturation time for dissolution and the saturated dissolution width of base metal decreased in the order; single crystal, coarse-grained and fine-grained base metals. The eutectic width decreased linearly with the square root of holding time during the isothermal solidification process for single crystal, coarse-grained and fine-grained base metals. The completion time for isothermal solidification decreased in the order; single crystal, coarse-grained and fine-grained base metals. The difference of isothermal solidification rates produced when bonding the different base metals could be explained quantitatively by the effect of base metal grain boundaries on the apparent average diffusion coefficient of boron in CMSX-2.
