Features of Spark Erosion Fine Powders of Mo and Nb Alloys

The characteristics of spherical powders of (Mo,Nb) and (Nb,Mo) alloys prepared by the spark erosion technique are described. Two modes ( U = 24 V, I = 10 A and U = 24 V, I = 20 A in distilled water) were chosen for powder preparation. The pyrolysis of the dielectric liquid during spark erosion leads to the formation of stable oxides NbO and NbO 2 as thin crusts and spherical inclusions from 10 nm to 10 μm in powder particles. The largest deviations from electrode compositions (from 3 to 7 wt % Nb) are inherent to Mo alloys with 9 and 10 wt % of Nb. The number of NbO and, to a lesser extent, NbO 2 inclusions in spherical powder increases with increasing Nb content in the alloy, but only in the series of (Mo,Nb) samples. Such regularity is not observed for (Nb,Mo) series. A decrease in current value results in a change in the granulometric compositions of spherical powders. The main fraction of powders at I = 20 A is 40–80 μm and I = 10 A is 20–50 μm.