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.
Highlights
Environmental demands on the generation of aero engines may require an increased service temperature
The thin-walled “wedge” castings fabricated and examined in this study are shown in Relatively high Ts and Tm temperatures were utilized during the casting process to obtain satisfactory filling of the thin-walled sections of the patterns
The chemical composition of the as-cast Haynes® 282® given in Table 1 reveals that the vacuum induction melting and investment casting (VIM IC)
Summary
Environmental demands on the generation of aero engines may require an increased service temperature. Turbine structural components are traditionally cast as single piece components, which are relatively expensive because of the low efficiency of the casting process and post cast operations. For this reason, the recent trend in fabrication of large structural components is to cast smaller parts which can be joined with rolled or forged parts. The recent trend in fabrication of large structural components is to cast smaller parts which can be joined with rolled or forged parts This provides the possibility to use higher strength wrought parts of relatively simple geometry with cast ones of complex geometry, which usually carry lower loads.
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