Abstract
An insert metal for liquid diffusion bonding of HP40 was newly developed by using a mathematical programming method. The main procedure of this method is to obtain the optimum composition to maximize some index of an performance of the insert metal by a grid search. The procedure also involves data estimation by means of the interpolation method which was originally proposed by Schagen. The contour maps of objective function Z which were introduced as the index of a performance of the insert metal were obtained through the interpolation method. The curved surface being once obtained, its general view would give suggestions for further searches and the optimum composition could be efficiently searched. As the results of the search, a composition of Fe-24Cr-33Ni-2.7B-1.5C-4Si which minimized the objective function was determined. Scanning electron microscopic analysis revealed that the joint bonded at 1473 K with the newly developed insert metal (Fe-24Cr-33Ni-2.7B-1.5C-4Si) had a sound microstructure without forming brittle phases in the bonding interlayer. This joint also exhibited good tensile properties, that is, its strength and ductility were comparable to those of the base alloy.
