Microstructure, mechanical properties and oxidation resistance of the Nb-Si-B type powder compacts prepared by spark plasma sintering

摘要

Spark plasma sintered compacts with eight different compositions of the Nb-Si-B system were prepared via the following three routes: (i) elemental powders were mixed in a hexane-filled ball mill and then sintered by spark plasma sintering method, (ii) elemental powders were mechanically alloyed and sintered similarly to (i), and (iii) blended elemental powders were pre-sintered, milled and sintered once again similarly to (i). Microstructure, mechanical properties and oxidation behaviors of each compact were investigated. Inhomogeneous microstructure was observed in the compacts prepared via the first route, while a large amount of oxide phases was observed in the compacts prepared via the second route. However; both homogeneous microstructure and a small amount of oxide phases were seen in the compacts prepared via the third route. The compacts with compositions around the line of Nb{sub}5Si{sub}3-Nb{sub}5Si{sub}3B{sub}2-NbB{sub}2 showed a high hardness at room temperature and a high compressive strength at high temperatures in comparison to those with compositions away from the line. The oxidation resistance of Nb{sub}5Si{sub}3B{sub}2 compact was superior to that of Nb{sub}5Si{sub}3 compact, but extremely worse than that of NbSi{sub}2 compact.