Dissolution and precipitation of carbide in hot-rolled Inconel alloy 690

Abstract

The behavior of carbide dissolution and precipitation in hot-rolled Inconel690 has been investigated by means of scanning electron microscopy. Transmission electron microscopy was employed to determine the type of carbide. The results show that more strip like carbide precipitates, identified as M23C6, distribute along grain boundaries in hot-rolled alloy 690 bars, and only few discrete particles present in the matrix. Dissolution temperatures of intergranular and intragranular carbides are 1050°C and 1080°C, respectively. The carbide particles in hot-rolled bar could not fully dissolve and some still existed at grain boundaries for low solution temperature, then these remained carbide particles really hindered the new carbide re-precipitation during the following thermal treatment at 715°C. However, to the clean grain boundaries after the carbides are fully dissolved at higher solution temperature, the newly fine and semi-continuous carbide precipitates can formed along the grain boundaries after following thermal treating.