Two-step sintering of molybdenum nanopowder

Abstract

Molybdenum is a potential material for applications in intense heat including the manufacture of aircraft parts, electrical contacts, and filaments, because it can withstand extreme temperature without significant degradation of its mechanical properties. Conventionally, Mo powder is sintered at high temperature over 1800°C in order to fabricate dense parts, due to its high melting point of 2610°C In this study, the nano-sized Mo powder was fabricated by high energy ball-milling and subsequent hydrogen reduction. A two-step process was employed for the sintering of Mo nanopowder to obtain ultra fine grain size in bulk parts. The densification over 90% could be obtained by the pressureless sintering of Mo nanopowder at 1300°C with a grain size of 1μm and a hardness value of 2.34GPa. The two-step sintering process restrained grain growth to 0.5 μm and consequently improved hardness up to 3.15GPa even though the density was 90% of the theoretical value.