PRESSURELESS SINTERING OF NANOGRAINED FE-(FE,MO)(6)C COMPOSITE POWDERS

High strength in two phase particulate composite materials can be achi eved by embedding a high volume fraction of ultrafine (preferably nano meter size) hard particles in a ductile metallic matrix. Prealloyed mi crometre sized iron powders, containing a high volume fraction (greate r than or equal to 0.52) dispersion of nanograined (Fe,Mo)(6) carbide, were produced by a novel spray conversion process, starting from wate r soluble precursors. The average grain size of both phases in the as synthesised powders was found to be 50 nm by X-ray line broadening. Th e effects of compaction pressure and sintering atmosphere on densifica tion, 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 improvem ents in hardness characteristics over conventional M2 steel.