Two step sintering of Molybdenum Nanopowder

Abstract

Molybdenum is a potential material for use at elevated temperatures since it shows excellent mechanical properties at high temperatures. Conventionally, Mo powder is sintered at temperature over 1800oC in order to fabricate dense parts due to its high melting point of 2610oC. In this study, the nano-sized Mo powder was fabricated by high energy ball-milling and subsequent hydrogen reduction. Two-step process was employed for the sintering of Mo nanopowder to obtain fine grain size in bulk part. The densification over 94% could be obtained by the pressureless sintering of Mo nanopowder at 1200oC for 1 h with 1.4 μm in grain size and the 2.34GPa in hardness. Moreover, the two-step sintering process led to restrain grain growth to 0.5 μm and to consequently improve hardness up to 3.15GPa even though the density was 90% of theoretical value.