Development of Single-Crystal Ni-Base Superalloys Based on Multi-criteria Numerical Optimization and Efficient Use of Refractory Elements

Abstract

The development of new Ni-base superalloys with a complex composition consisting of eight or more alloying elements is a challenging task. The experimental state-of-the-art development cycle is based on the adaption of already existing compositions. Although new alloy compositions with potentially improved material properties are expected to be similar to already known superalloys, this procedure impedes efficiently finding these compositions in the large multi-dimensional design-space of all alloying elements. Modern alloy development combines numerical optimization methods with experimental validation to guide the development towards promising compositions. In this work, an improved numerical multi-criteria optimization tool using CALPHAD calculations and semi-empirical models for alloy development is presented. The model improvements to its predecessor are described and the successful application for the development of rhenium-free single-crystal Ni-base superalloys ERBO/13 and ERBO/15 is revisited. The optimization tool is described and the designed alloys are discussed regarding phase stability. Finally, a possible phase stability model extending the optimization tool and improving the alloy composition predictions is presented.

Composition rules of Ni-base single crystal superalloys and its influence on creep properties via a cluster formula approach

“…Several computation-aided design methods have been applied into the development of Ni-base SC superalloys, such as PHACOMP (a phase computation method based on the electron vacancy concept) 28 – 30 , New PHACOMP based on the d -electrons theory 31 – 34 , ADP (an alloy design program based on a mathematical model using regression equations in microstructure and property databases) 14 , 35 , Multi-criteria Numerical Optimization (an improved numerical multi-criteria optimization tool using CALPHAD calculations and semi-empirical models) 36 , 37 , Alloys-by-Design (a design model by incorporating the complex interactions among alloy composition, microstructure and processing) 38 , 39 , and so on. Among them, the classical New PHACOMP was well developed by calculating the electronic structure of alloys with the DV-Xα molecular orbital method, in which the important parameter represents an average energy level of d orbitals of transition metals and is used to predict the phase stability of FCC-γ matrix and the precipitation of TCP phase 31 – 34 .…”

The Importance of Diffusivity and Partitioning Behavior of Solid Solution Strengthening Elements for the High Temperature Creep Strength of Ni-Base Superalloys

“…Consequently, the calculation of the partitioning behavior and the resulting interdiffusion coefficient is an useful parameter for the evaluation of the high-temperature creep strength of single crystalline Ni-base superalloys in optimization tools for alloy development. [52] V. CONCLUSION Nine derivatives of the Astra2-Base alloy containing different solid solution strengtheners (Ir, Mo, Re, Rh, Ru, Re, W) were investigated to understand the influence of solid solution strengthening elements on the high-temperature creep strength of Ni-base superalloys at 1373 K (1100°C). Special emphasis was placed on the partitioning behavior and interdiffusion coefficient of the alloying elements.…”

Evolution of Microstructure and Mechanical Properties of ATI 718Plus® Superalloy After Graded Solution Treatment

“…In the modern world, conventional heat treatment optimalization methods are not cost-effective and time consuming. Thus, highly efficient methods in materials science are desired, whether it is a computational [28,29] or experimental [30] alloy design. The present work focuses on the application of heat treatment with gradient temperature for a 1-hour solution treatment of 718Plus superalloy in a wide range of temperatures.…”