Modelling the coefficient of thermal expansion in Ni-based superalloys and bond coatings

Abstract

The coefficient of thermal expansion (CTE) of nickel-based superalloys and bond coat layers was modelled by considering contributions from their constituent phases. The equilibrium phase composition of the examined materials was determined using thermodynamic equilibrium software with an appropriate database for Nibased alloys, whereas the CTE and elastic properties of the principal phases were modelled using published data. The CTEs of individual phases were combined using a number of approaches to determine the CTE of the phase aggregate. As part of this work, the expansion coefficients of the superalloy IN-738LC and bond coat Amdry-995 were measured as a function of temperature and compared with the model predictions. The predicted values were also validated with the published data for the single-crystal superalloy CMSX-4 and a number of other Ni-based alloy compositions at 1000 K. A very good agreement between experiment and model output was found, especially up to 800 C. The modelling approaches discussed in this paper have the potential to be an extremely useful tool for the industry and for the designers of new coating systems.

Mathematical Processing and Structural Explanation of Surface Tension Polythermal Diagram Reached Out to Achieve Critical Temperature of Thermo-time Treatment for a Ni Based Superalloy

“…Principle scheme of the pilot unit for measuring the surface tension by the maximum pressure in gas bubble method for a metallic melting,super alloy 7045 MSRR, particularly, is shown in figure 2, [1,4].…”

“…The ideas underlying genetics, metallurgical heredity respectively, appeared in more than 50 years ago in different references [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In the broad metallurgical sense heredity is the description of those properties of metals that are not only based on status, but depend on their past [3].…”

Phase composition of Ni-Al-Co-Me-based superalloy modified by deformation

“…According to Fig. 3 (b, c) the -phase reflections are observed on microdiffraction patterns along with the reflections of '-phase [9][10][11][12]. In the alloy obtained by the directional crystallization, -phase with the hexagonal close-packed (HCP) crystal lattice is observed.…”

Modelling of microstructural evolution in multi-layered overlay coatings

“…A modelling capability that can predict microstructural evolution processes in coating structures is extremely valuable and can assist the development process of advanced coating systems such as SMART coatings. The development of a microstructural simulation model for coated superalloy systems was reported earlier [12], and the model was validated against a number of experimental single-layered coating systems [12,13]. In this work, the capability of the model has been extended further to incorporate multi-layered coatings and the developed model is used to examine the thermal stability of a trial, functionally graded, multi-layered coating system from an early stage of a coating development process.…”

“…Computer modelling has been successfully applied in many areas of nickel-based superalloys such as thermodynamics [6][7][8], solidification [9,10], microstructural evolution [11,12] and prediction of physical properties [10,13]. A modelling capability that can predict microstructural evolution processes in coating structures is extremely valuable and can assist the development process of advanced coating systems such as SMART coatings.…”