The structure and properties of pre-alloyed NiAl-Cr(Co,Hf) spherical powders produced by plasma rotating electrode processing for additive manufacturing

Abstract

The structure and properties of pre-alloyed Ni41Al41Cr12Co6 spherical powders (the 40–160 μm fraction) produced using the plasma rotating electrode processing technology were studied. The evolution of the fine structure of pre-alloyed Ni41Al41Cr12Co6 spherical powders under heating at 20, 350, …, 850 °C was investigated. Disk-shaped chromium-rich pre-precipitation zones 5–30 nm in size were detected in the temperature range of 450, …, 650 °C; they precede the formation of the dispersed chromium precipitate. Prism-shaped chromium nanocrystals with the characteristic longitudinal dimension ranging from 15 to 100 nm, whose nucleation process starts at prismatic dislocation loops, were found to be formed at 750, …, 850 °C. The Young's modulus, hardness, and elastic recovery of powder material were determined by nanoindentation measurements. The resulting powders are characterized by bulk density of 3.8 g/cm3, excellent flow rate (3.5 s), and the angle of repose of 19.6°. Keywords: Plasma rotating electrode processing (PREP), Spherical powders, Nickel aluminide, Precipitation hardening, Intermetallic alloys, Nucleation and growth