Search Results for soft X-ray emission spectroscopy

Interstitial carbon (C) in β-Ti, α-Ti, α 2 -Ti 3 Al and γ-TiAl phases present in the γ-TiAl alloys with and without substitutional elements (M: transition element) is quantitatively analyzed using soft X-ray emission spectroscopy (SXES), in order to reveal the effect of solute carbon on the phase equilibria. SXES for carbon analysis was used and the peak intensity of the second reflection of carbon Kα is analyzed using the fully homogenized sample having different C content under the optimum condition to make the accurate calibration curves. The obtained calibration curve is in an accuracy of ± 0.07 at. % C. In all heat treated alloys, no carbide is observed. In Ti-Al binary system, the α+γ phase region shifts toward higher Ti side, and the volume fraction of γ phase increases slightly with the carbon addition. In all system, carbon preferentially partitions into the α phase, followed by less partitioning in the γ and β phases in order. The carbon content in the β phase remains unchanged of almost 0.05 at. % regardless of carbon addition in Ti-Al-V system and the partition coefficient of carbon between the α and γ phases becomes larger in Ti-Al-V system than that in TiAl binary system.

This study investigates the steam oxidation behavior of Alloy 699 XA, a material containing 30 wt.% chromium and 2 wt.% aluminum that forms protective oxide scales in low-oxygen conditions. The research compares four variants of the alloy: conventional bulk material, a laser powder bed fusion (LPBF) additively manufactured version, and two modified compositions. The modified versions include MAC-UN-699-G, optimized for gamma-prime precipitation, and MAC-ISIN-699, which underwent in-situ internal nitridation during powder atomization. All variants were subjected to steam oxidation testing at 750°C and 950°C for up to 5000 hours, with interim analyses conducted at 2000 hours. The post-exposure analysis employed X-ray diffraction (XRD) to identify phase development and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) to examine surface morphology, cross-sectional microstructure, and chemical composition. This study addresses a significant knowledge gap regarding the steam oxidation behavior of 699 XA alloy, particularly in its additively manufactured state.

Alumina-forming austenitic stainless steels (AFAs) are potential materials for boiler/steam turbine applications in next generation fossil fuel power plants. They display a combination of good high temperature creep strength, excellent oxidation resistance and low cost. A recently-developed AFA alloy based on Fe-14Cr-32Ni-3Nb-3Al-2Ti (wt.%) shows better creep performance than a commercially-available Fe-based superalloy. In this paper we used scanning electron microscopy and transmission electron microscopy to study the fracture surfaces and cracking behavior in relation to the precipitates present in creep failure samples of this alloy tested at either 750°C/100 MPa or 700°C/170 MPa. It was found that most cracks are formed along the grain boundaries with precipitate-free zones beside the grain boundaries potentially providing the path for propagation of cracks.