The kinetics of grain boundary carbide precipitation in Nimonic PE16

Abstract

Experimental isothermal grain boundary precipitation curves for Nimonic PE16 have been determined over a range of temperature between 625 and 900°C. They show that TiC is the stable grain-boundary precipitate above 800°C while M₂₃C₆ precipitates on grain boundaries below 800°C. A theoretical model has been developed to apply specifically to grain boundary carbide precipitation in this alloy and this gives reasonable fits with the experimentally determined curves. The model further indicates that to predict the observed TiC precipitation behaviour grain-boundary segregation of titanium to approximately five times the matrix composition is required.