Die Wall - Vs. Bulk Lubrication in Warm Die Compaction: Density, Microstructure and Mechanical Properties of Three Low Alloyed Steels

The influence of die wall lubrication during warm die compaction on densification, microstructure and mechanical properties of three low alloy ferrous powders was investigated. Specimens were sintered at 1250°C. Die wall lubrication leads to higher green and sintered density and enhances the dimensional stability. It does not affect the microstructure of the matrix, while pores are smaller and more rounded than in bulk lubricated specimens. In TRS tests, both strength and deformation are higher in die wall lubricated specimens than bulk lubricated ones.

Die Wall Lubricated Warm Compaction of Fe-Ni-Cu-Mo-C Powders

The combination of warm compaction and die wall lubrication, called die wall lubricated warm compaction was used to make Fe-Ni-Cu-Mo-C powder metallurgy material. Results showed that the green density could be 7.38 g•cm-3 under the pressure of 700MPa at the temperature of 120°C. The sintered density could be 7.34 g•cm-3 and dimension change was 0.19% when sintered at 1200°C for 50 minutes. Both green density and spring back effect gradually increased as the compacting pressure rose. The relation between compacting pressure and green density could be described by Huang Pei-yun double logarithm equation. Different forming conditions effecting green density in turn from big to small were compacting pressure, lubrication, compacting temperature, mixing method and compacting speed.

Development of High Strength Sintered Steel by High Pressure Warm Compaction Using Die Wall Lubrication

The high pressure compaction without internal lubricant and the high green density even with the pore free density were achieved by the newly developed die wall lubricant for warm compaction. This developed die wall lubricated warm compaction followed by high temperature sintering resulted in improved mechanical property and almost no dimensional change. In this paper, the effects of increasing the green density on the sintered density, the dimensional change and the mechanical property are mainly discussed.