Microstructure of Haynes® 282® Superalloy after Vacuum Induction Melting and Investment Casting of Thin-Walled Components

Abstract

The aim of this work was to characterize the microstructure of the as-cast Haynes® 282® alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray spectroscopy (EDS), wave length dispersive X-ray spectroscopy (WDS), auger electron spectroscopy (AES) and electron energy-loss spectrometry (EELS). The phases identified in the as-cast alloy include: γ (gamma matrix), γʹ (matrix strengthening phase), (TiMoCr)C (primary carbide), TiN (primary nitride), σ (sigma-TCP phase), (TiMo)2SC (carbosulphide) and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm), while coarser (113 nm) cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN), are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC), preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo)2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix.

Comparison of Creep Properties of Cast and Wrought Haynes 282 Superalloy

“…However, the TEM images in Figure 9 show homogeneously distributed c′-particles with a globular shape in the cast alloy before creep, so the results of Sajjadi et al [10] are not applicable to this study. e average size of the precipitates was 39 nm, which is smaller than that reported by Matysiak et al [5] (70-110 nm), who investigated the same alloy directly after thin-walled wedge permanent casting in which coarsening of c′-particles occurred. In this study, however, c′-particles fully dissolved during solution treatment after casting; a dense precipitation of nely distributed c′-particles formed during the two-step ageing treatment following by quenching.…”

“…e particles observed in the grain interiors and grain boundaries are MC-type carbides, such as (Ti,Mo)C; Cr-rich carbides (presumably M 23 C 6 ) precipitated preferentially in interdendritic regions and grain boundaries. Matysiak et al [5] investigated the cast microstructure of the same alloy and reported that the secondary phases were mostly (Mo/Cr)-rich carbide and the c′-phase of (Ni, Ti)Al. ey also reported that the c′-phases precipitated as a round shape (size: 70 nm) in dendritic regions and as a cubic shape (size: 110 nm) in interdendritic regions.…”

Microstructure and Hardness Evolution in Haynes 282 Nickel-Based Superalloy During Multi-variant Aging Heat Treatment

“…Haynes 282 is classified as c¢-strengthened wrought superalloy (but, it is also under consideration as a cast alloy for fabrication of casings and thin-walled components (Ref 4,5)). Its mechanical properties are controlled by the heat treatment containing the solutionizing followed by aging processes.…”

Weldability of Ni-Based Superalloys Waspaloy® and Haynes® 282® - A Study Performed with Varestraint Testing

“…The microstructural analyses of the HAZ reveled possible evidence of a secondary phase distributed ahead of the propagating cracks in the Haynes® 282® samples. This secondary phase can be the same as distributed interdendritically in the FZ identified in other studies [5,16] as Ti-Mo based MC-type carbides with an FCC crystal structure. MC carbides were found randomly distributed intergranularly and intragranularly within γ phase with typical size in the range of 2-15 µm.…”