Primary carbides in alloy 718

This study presents the effects of long term homogenisation at 1200C on the as-cast structure of alloy 718 in terms of the size distribution of the primary carbides. We find that the size distribution changes slightly over the first 20h of treatment, following a solution of some of the carbide, but that it does not change significantly over the next 180h, indicating a rapid process of following the solution equilibrium at temperature. The effect is also reported in relation to the melting of an electrode of the same structure during the VAR process. It is found that the as-cast structure of the electrode used in VAR does not influence the structure of the VAR ingot in respect of primary carbide size distribution. (AU) © 2010 by The Materials, Metals, & Materials Society. All rights reserved.