Studies on the synthesis and characterization of a molybdenum-based alloy

The excellent high temperature strength and thermal conductivity of molybdenum-based refractory alloys provide them attractive features for application as structural components in hot working areas. However, synthesis of these alloys through conventional melting route pose the problems of segregation and inhomogeneous melting due to large difference in melting temperature of molybdenum and other alloying components. In the present investigation, attempts were made to synthesize a typical molybdenum-based alloy, popularly known as TZC alloy with nominal composition, Mo–1.2Ti–0.3Zr–0.25C (wt.%) from the oxide intermediates, MoO2, TiO2 and ZrO2 by their simultaneous co-reduction with aluminium in presence of requisite amount of carbon. The oxide intermediate of MoO2 was freshly prepared for use due to its unstable nature. Although the synthesis of the alloy was highly energy intensive due to high melting temperature of molybdenum, however, the thermal energy derived from the oxide–metal chemical reactions was effectively utilized to prepare the alloy in an off-furnace manner with satisfactory alloy yield. A typical charge composition containing 131 g MoO2, 4 g TiO2, 1.33 g ZrO2, 10 g CaO, 1.0 g C and 49.21 g Al (specific heat ∼3220 kJ kg−1) resulted in TZC alloy product with 84 wt.% yield. As-reduced alloy was subsequently homogenized and consolidated by arc melting technique and purified by electron beam melting technique. The alloy after consolidation and purification had exhibited composition nearly matching the desired composition. The alloy was further characterized with respect to composition, phases, and microstructure. The properties such as hardness and oxidation behaviour were also evaluated.