Features of spark erosion fine Mo and Nb alloys powders

Сharacteristics of spherical powders of (Mo,Nb) and (Nb,Mo) alloys prepared by spark erosion technique are described. Two regimes (U = 24 V, I = 10 A and U = 24 V, I = 20 A in distilled water) were chosen for powder preparation. The pyrolysis of dielectric liquid during spark erosion leads to the formation of stable oxides NbO and NbO2 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 NbO2 inclusions in spherical powder increase with increasing of Nb content in alloy, but only in series of (Mo,Nb) samples. Such regularity is not observed for (Nb,Mo) series. Decrease of current value results the change of 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.