• Highly alloyed gas atomised Ni-base superalloy powders are utilised in diverse bulks forming processes of AM, WGB and HIP. • The trace amount γ′ and properties of powders are studied by combining synchrotron XRD and nano-indentation. • Coarse powders exhibit hardness similar to relative bulk alloys and 23 ∼ 40 % harder than fine powders with faster cooling. • Hardness correlation established between powder/bulks and existing wrought, cast and PM superalloys. • Ultrafast cooling of 10 5 ℃/s inhibits the γ′ precipitation and result in softer fine superalloy powders. An investigation was conducted on gas atomised (GA) highly alloyed Ni-based superalloy powders utilised in diverse processes including additive manufacturing (AM), wide gap brazing (WGB) and hot isostatic pressing (HIP). The microstructure and nano-mechanical properties of raw powders with different particle size ranges (Ф<32 μm, 100–150 μm) have been investigated using combined characterisation methods of high energy synchrotron X-ray diffraction (HESXRD), dual beam FIB, transmission electron microscopy (TEM) and nano-indentation (NI), and then compared with their respective bulk alloy counterparts. The results indicated that precipitation of nano-scale γ′ phases and MC carbides were presented in coarse powders, while only trace amount of these phases was detected in fine powders. The cooling rate (10 5 ℃/s) of fine powders, which exhibit the lowest hardness, is 2 to 5 orders of magnitude higher than that of the GA coarse powders and AM/WGB/HIP bulk alloys. Coarse powders possess hardness value of 8.61 GPa, which is similar to AM (8.70 GPa), WGB (8.19GPa) and HIP (9.32GPa) bulk alloys, and harder than that of the fine powders (6.65GPa). This finding provides evidence of γ′ phases existence in rapidly solidified Ni-based superalloy powders, and highlights their significant impact on properties of both the powders and the resulting bulk alloys.
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Zheng et al. (2025) studied this question.