Cubic compacts, 10 mm in size, were formed from an electrolytic powder with a die-wall lubricant alone, or with 0.7 wt% of Ca, Fe or Zn stearate to change the swelling during the de-waxing operation. Some compacts were compressed slightly in a lateral direction after the ejection from the die to simulate the spring-back. The dimensions of the compacts were measured with a micrometer i) during the production process, ii) during the pressing operation at 588 MPa, iii) after ejecting, iv) after de-waxing at 600°C (873 K) for 30 min and v) after sintering at 1100°C (1373 K) for 60 min in dissociated NH3.
The compressed compacts containing Zn stearate showed residual expansions in two other directions, larger in the compacting direction and less in the non-compressed lateral direction. The compacts with Ca stearate swelled remarkably while dewaxing, especially in the compacting direction, while other lubricants caused some shrinkage. All compacts except those containing Ca stearate which shrank while holding at 1100°C (1373 K) shrank mostly during the heating operation in the upper α temperature range.
A good proportionality was found between the expansion from the minimal dimension to the maximal dimension before sintering and the shrinkage from the maximal dimension to the dimension of the sintered compact regardless of the direction.