Two step sintering of ball milled nanopowder

Abstract

Molybdenum is potential material for applications in harsh environment such as aircraft parts, electrical contacts, and filaments because it can withstand extreme temperature without significantly degrading mechanical properties. In this study, the nano-sized Mo powder was fabricated by high energy ball-milling and subsequent hydrogen reduction. Two-step sintering was introduced to the densification of Mo nanopowder to obtain sintered body with ultra fine grain. The densification over 90% could be obtained by the pressureless sintering of Mo nanopowder at 1300oC with 1.0μm in grain size and the 2.43GPa in hardness. 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.