Fabrication of high temperature oxides dispersion strengthened tungsten composites by spark plasma sintering process

Abstract The paper describes the fabrication process of high temperature oxides, such as Y 2 O 3 , HfO 2 and La 2 O 3 , dispersed tungsten composites by spark plasma sintering. The oxide contents varied from 0 to 5 wt% and sintering was conducted for 3 min at 1700 °C. Among three kinds of oxides, Y 2 O 3 is the most efficient element to consolidate W powder. As dispersed up to 5 wt% Y 2 O 3 into the matrix, the relative density of the W composite is increased up to nearly 100% of theoretical value. In order to analyze the effect of Y 2 O 3 particles on the densification of W powders, the microstructure of W–Y 2 O 3 composite is observed using the transmission electron microscopy. By this experiment, it is found that dark phases, which had been known as Y 2 O 3 phase, are composed of W, Y and O. Therefore, during sintering, W atoms move through Y 2 O 3 phases as well as W grain boundaries, thereby W and Y 2 O 3 are soluble, and so sinterability of W is enhanced. The hardness of the composite is increased from 350 to 510 kg/mm 2 with increasing Y 2 O 3 contents since the relative density is increased and the grain size is reduced from 20 to 4 μm. However, in case of HfO 2 and La 2 O 3 , the hardness of the composites is decreased even though the grain size is reduced because of their lower relative densities.