Effect of solidification conditions on MC carbides in a nickel-base superalloy IN 738 LC

Abstract

Transition metal carbides (MC) formed in the solidification process of cast nickel-base superalloys were found to affect greatly the mechanical properties and boundary performance of alloys. Thus, investigations of their growth behavior have received considerable concern from metallurgists. Earlier studies on such carbides were mostly confined to normal solidification conditions, i.e. equiaxed and directionally solidified conditions. Recently, some researchers also investigated the carbides with the rapid solidification method. However, there is lack of systematic study of growth characters of MC carbides under various solidification conditions. The intent of this paper is to establish a complete description for carbide growth. Accordingly, the variations of morphology, size, amount and distribution of MC carbides in the nickel-base superalloy Inconel 738 LC will be studied under a broad range of cooling rates from 10[sup [minus]2] to 10[sup 5][degree]C/s by use of directional solidification, investment casting, chill casting and splat cooling methods.