Surface precipitate analysis of gas atomized Ni-Base superalloy powders

Abstract Powders surface precipitate has strong relations with the microstructure and properties of powder metallurgy components. Morphology, element distribution and crystal structure of the precipitate at gas atomized Ni-base superalloy powders surface were investigated. Results show that the precipitate is lamelliform and prefers to form at grain boundaries and interdendrite regions than dendrite arms. With powders size decreasing, the precipitate shape observed from surface varies from strip to rectangular and to nearly round, and the precipitate density increases, measured 17.75 μm −2 , 21.42 μm −2 , 26.50 μm −2 at nearly 45μm, 30μm and 10μm powders surface respectively, but the precipitate average size changes conversely, that is 228nm, 193nm, 77nm respectively. The precipitate enriches in high melting point elements Ti, Nb, Mo, W, Zr and poor in low melting point elements Ni, Cr, Co, Al. Crystal structure analysis reveals that the precipitate is MC, M 23 C 6 or M 6 C carbide.