Abstract
The dimensional changes during compacting and sintering were measured. Less than 5 mass% of copper was added to the Hoeganaes NC100.24 iron powder, as electrolytic powder, or as a coating by the substitution-precipitation process, or as 20 mass%Cu Distaloy powder. They were further mixed with 0.7 mass% of zinc stearate and pressed under 490 MPa to form compacts 10 mm in diameter and 10 mm in height. The compacts were dewaxed by heating at the rate of 50 K/min up to 873 K, being held for 30 min, and sintered successively by heating at the rate of 30 K/min up to 1398 K and being held for 30 min in dissociated ammonia.
No effects of techniques for copper addition were found on the spring-back during compacting. The dimensional changes obtained after sintering generally indicated a tendency to expansion with an increase in the copper content. The coated powder had an almost constant difference between the dimensional changes in the compacting and in the lateral directions, though the mixed powder had an increasing tendency to expansion with an increase in the copper content in the compacting direction.
