Development of Nickel Based Superalloys for Advanced Turbine Engines

Superalloys have been developed for specific, dedicated properties and applications. One of the main application for this material is advanced, high-performance aircraft engines elements. Turbine engine creates harsh environments for materials due to the high operating temperature and stress level. Hence, as described in this article, many alloys used in the turbine section of these engines are very complex and highly optimized. This article provides an overview of structural changes that occur during the aging process of wrought and cast alloys and provides insight into the use of precipitated particles to achieve desired structures. Example will focus on alloy Inconel 718 and CMSX-4. Functional properties of these alloys can be achieved by choosing proper heat treatment parameters to obtain required rate between secondary phases. The paper also attempts to determine structural perfection and changes of crystallographic orientation along the axis of growth of single crystal nickel superalloys cast using X-ray topography and Laue diffraction method. Single crystal bars and turbine blades were manufactured in VIM furnace using the Bridgeman method. Withdrawing rates typical for CMSX-4 superalloy were used. It has been found that with increasing withdrawing rate the nature of distribution along the axis of growth of the angle of [001] direction deviation from the axis of single crystal blades growth had changed. The change of the withdrawing rate results also in the rotation of γ’ phase in the form of cubes against the axis of single crystal blades growth.