Densification during the supersolidus liquid-phase sintering of nickel-based prealloyed powder mixtures

This article examines densification during supersolidus liquid-phase sintering (SLPS) of a mixture of two nickel-based prealloyed powders. The two powders were of similar compositions, where one powder alloyed with boron had a lower melting-temperature range than the other. Sintering of such binary powder systems is performed at temperatures above the solidus of the low-melting powder, to form a liquid phase that promotes densification. Measurements of shrinkage, sintered density, and melting were used to determine the densification mechanism. An increase in the fraction of the high-melting powder resulted in retardation of sintering. A densification model based on viscous flow was developed using rheological principles. The model is a first step in the extension of the conventional models of densification of single prealloyed powders to ones of mixtures of prealloyed powders. It incorporates the effects of homogenization between the two powders, specifically, the diffusion of boron from the low-melting to the high-melting powder. The densification of the powder mixture was found to depend on the extent of melting of the low-melting powder and the fraction of the high-melting powder.