Design of a rapidly sintering Mo-W-Cr alloy

Abstract

Mo-W based materials have excellent mechanical and thermal properties, but are difficult to produce and require either very high temperatures or complicated sintering procedures, and typically have coarse structures. Here the nanophase separation sintering (NPSS) design criteria are used to develop a rapidly sintering ternary Mo-W based alloy. A composition of Mo-25 W-15Cr is chosen and shown to exhibit the critical features of NPSS. The relevant sintering temperatures are shown to be much lower than for comparable refractory alloys. The kinetic mechanisms that facilitate the enhanced sintering are verified, and these involve the transient precipitation and redissolution of a second phase that accelerates sintering. That second phase is fully eliminated at the end of sintering, permitting potential usage of the alloy at temperatures above the sintering range. Finally, the resulting hardness of the material is compared to that of Mo-W alloys produced through other methods, showing a significant strength boost due to the rapid low-temperature sintering and its attendant fine microstructure.