The effects of green density and sintering time on various properties of sintering Fe-20% Cu with and without graphite addition were investigated. Sintering was carried out at 1140℃ in hydrogen atmosphere. The specimens were cylindrical ring shape and dimensional changes in O.D. and I.D. after compacting and sintering were carefully measured and compared.
Fe-20% Cu compacts showed rapid growth during first 10 minutes of sintering with subsequent densification. The samples with higher green density showed larger dimensional growth and smaller shrinkage during the initial and subsequent stages of sintering. Observations of the microstructures indicate that the results can be best explained by the penetration of the iron particle boundaries by liquid copper at the beginning of the sintering process.
Addition of graphite reduces the growth but has little effect on the shrinkage.
The effects of green density and sintering time on degree of oil impregnation and radial crushing strength were also investigated. The results closely follow general expectations. With increased sintering time the amount of open porosity decreased while the closed porosity did not show much change.
