DIMENSIONAL CONTROL IN THE SINTERING OF IRON-COPPER-CARBON VIA PARTICLE SURFACE-AREA

A large portion of powder metallurgy centers on the production of prec ise ferrous parts via die compaction. One of the most common alloy sys tems is iron-copper-carbon, which is extensively used in the automobil e industry. Unfortunately these alloys are known to exhibit undesirabl e swelling during sintering, thereby lowering dimensional accuracy Swe lling in iron-copper alloys is mainly the result of copper wetting the grain boundaries and pushing the iron grains apart. In addition, swel ling in iron-copper alloys varies inversely with the powder surface ar ea. Therefore, this research focuses on the elimination of swelling by modifying the surface area of the iron powder: This was accomplished by mixing water atomized iron powder with other iron powders (a water atomized a sponge, and a carbonyl iron). Two mixtures were developed w hich exhibited zero dimensional change, without significant losses in sintered properties. After copper infiltration, both mixtures showed b etter tensile properties than the unmodified powder mixture.