Compaction and Sintering Behavior of Niobium Powder for Making Consumable Electrodes

Niobium consumable electrodes of 10 mm dia x 50 mm length were prepared by cold isostaic pressing with compaction pressure of 125-250 MPa. The compacts were sintered under vacuum at different temperatures in the range of 1000-1800 A(0)C. The CIPed and sintered electrodes were characterized with respect to chemical analysis, density, microstructure and bend strength. The results showed that there is a marginal improvement in density at a sintering temperature in the range of 1000-1400 A(0)C, while a significant improvement in density was observed at sintering temperature in the range of 1600-1800 A(0)C. The bend strength of sintered electrode was found to increase with increasing sintering temperature and that attains a highest value at a sintering temperature in the range of 1600-1800 A(0)C. Sintering at a temperature higher than 1400 A(0)C leads to decrease in oxygen content of the electrodes. The oxygen content was decreased from 2000 to 500 ppm when electrode was sintered at 1800 A(0)C.