Effects of atomizing condition on surface characteristics of nitrogen atomized Alloy 625 (high Ni alloy) powder and properties of the consolidated material have been investigated. The surface characteristics of the gas atomized powder depend largely upon the cooling rate after solidification even in an inert gas atmosphere. The amount of desorbed water increases with decreasing the powder size, whereas the dependence of cooling rate after solidification on the water content is negligibly small. The adsorbed water on the powder surface can be desorbed by evacuation at elevated temperatures. In addition, especially in case of slow cooling, significantly large amounts of oxides and/or hydrides, such as Cr2O3, Nb2O5, Ni(OH)2, are formed resulting in blowholes in the welding process of the consolidated material. Finally we have confirmed that the consolidated material of rapidly cooled gas atomized powder encapsulated and evacuated at 400°C has no blowhole in the welded metal. The tensile test and impact testing give almost the same results as the wrought materials.
