Development of Tungsten Based Alloy Through Nano Structuring

Abstract

Tungsten based alloys are extensively used in the defence application due to their high density and ability to withstand very high temperature. Solid state processing of pure and W based alloys is, however, a difficult task due to the high sintering temperature (2700°C) required to sinter them. Liquid phase sintered W heavy alloys has been used as penetrators, but they can’t be used for applications above 1200°C. Recently has shown that the sintering temperature of pure W could be brought down to ~1800°C from the conventional 2700°C by making the W-powder nanostructured prior to sintering. Present work aims at developing Oxidation resistant W-based refractory alloys through mechanical alloying is followed by solid state sintering at modest temperature. Proper sintered alloys has to be studied. Sintered density of W50Mo50 after sintering for 300 min at 1500°C was 92.5%, and it could be considered as a very significant extent of densification at this relatively low temperature, when compared to conventional sintering of microcrystalline W at 2700°C or above. Mechanical properties viz., hardness and elastic modulus of sintered W, determined by Nanoindentation tests, have been nearly similar to that of the conventional sintered W. The crystallite size and lattice strain of the nanostructured powders have been calculated from the X -ray diffraction patterns by Williamson-Hall method. Results of analysis showed that crystallite size of elemental W powder could be brought down to 40 nm after five h of ball milling. But further milling caused a significant level of contamination from the grinding media indicating severe work hardening of nanostructured W