Effect of die wall lubrication on warm compaction powder metallurgy

Die wall lubrication was applied on warm compaction powder metallurgy in the hope to reduce the concentration level of the admixed lubricant, since lubricant is harmful to the mechanical properties of the sintered material. Iron-based samples were prepared by die wall lubricated warm compaction at 135 and 175 °C, using polytetrafluoroethylene (PTFE) emulsion as the die wall lubricant. Compacting pressures of 700 and 550 MPa were used. An admixed lubricant concentration ranging from 0 to 0.6 wt.% was used in this study. The results show that in addition to a decrease in ejection forces, the green density of the compacts increased linearly with the decrease in the admixed lubricant content. The mechanical properties of the sintered compacts increase sharply when the admixed lubricant concentration was reduced to 0.125 wt.% or less. No scoring was observed in all of the experiments.