Study of conditions for obtaining precursors from heat-resistant NiAl-based alloy intended for 3D technologies

This article is the second in a series of articles devoted to studying the possibilities of preparing high-quality powder materials from heat-resistant light alloys based on refractory monoaluminides of nickel (β-NiAl), ruthenium (β-RuAl) and the FeCrAl system (fechrals) for the production of compact samples/products of complex shapes using additive technologies with minimal final machining. Additive technologies are based on the use of spherical precursor micropowders with a regulated granulometric composition, good fluidity and an oxide-free surface. In the first article, the possibilities of obtaining precursors from RuAl-based alloys by plasma spheroidization of powders obtained by crushing mixtures from scrap samples of RuAl-based alloys with various additives were considered. This article examines the possibility of obtaining precursors from NiAl-based alloys by plasma spheroidization of powders obtained by crushing mixtures from scrap samples of NiAl-based alloys with various additives. It has been shown that grinding and subsequent grinding of scrap powders in an attritor makes it possible to obtain precursors using the “attrition + plasma spheroidization” scheme with characteristics that make them suitable for additive manufacturing (perfectly round shape, surface almost free of oxides, phase composition – solid solution grains on based on NiAl with thin layers of Ni3Al of nano-sized thickness). The non-uniform distribution of alloying elements in NiAl grains is caused by the short duration (5 hours) of grinding the initial powders of scrap ingots of various compositions obtained using foundry technology. This can be corrected by increasing the grinding duration to 15 hours, which will require the use of the “attrition + granulation + plasma spheroidization” scheme, since the proportion of dispersed powders that must be included in circulation will increase. It has been shown that preliminary reaction alloying in the liquid phase (vacuum arc melting), including the use of recycled materials (scrap alloy samples) as starting materials, allows one to vary the alloy compositions over a wide range, using small volumes of material, and does not require specialized equipment.