Pressureless Sintering of Nanograined Fe—(Fe, Mo)₆C Composite Powders

Abstract

High strength in two phase particulate composite materials can be achieved by embedding a high volume fraction of ultrafine (preferably nanometersize) hard particles in a ductile metallic matrix. Prealloyed micrometre sized iron powders, containinga high volume fraction (≥0·52) dispersion of nanograined (Fe, Mo)₆ carbide, were produced by a novelspray conversion process, starting from water solubleprecursors. The average grain size of both phases in the as synthesised powders was found to be 50 nm by X–ray line broadening. The effects of compaction pressure and sintering atmosphere on densification, as well as the formation of a structure in which the two phases are continuous, are described. Hot hardness measurements on these high volume fraction carbide strengthened alloys show significant improvements in hardness characteristics over conventional M2 steel. PM/0653