Microstructural characterization and mechanical properties of Nb-Ti-C-B in-situ composites with W addition

Nb-Ti-C-B in-situ composites with W addition were fabricated by arc-melting method under an argon atmosphere. The microstructure and mechanical properties of the composites at room and high temperature were investigated, and the strengthening mechanism of W-added composites was discussed in detail. Microstructural observation shows that the composites contain primary Nbss dendrites and interdendritic eutectic network, and W addition refines primary Nbss and coarsens boride phase. The hybrid (Nb,Ti,W)C and (Nb,Ti,W)B second-phases are formed in the eutectic network of W-added composites. The hardness, room- and high-temperature compression properties were evaluated to determine the strengthening effect of W-added composites. The results indicate that the hardness and compressive strength of the composites are improved by W addition, which increases with increasing W content. Though the compressive strength of the composites decreased at 1200 °C, the increased W content was beneficial to high temperature strength improvement. The strengthening effect of W-added composites is mainly attributed to solid solution and grain refinement strengthening.