Dilatometric analysis of thermal debinding of injection moulded iron compacts

The less than desired tolerance control of powder injection moulded compact s is a result of inconsistent dimensional changes in the compacts accumulat ed during moulding, debinding, and sintering. This study investigated the i n situ length changes and their causes during thermal debinding on compacts which have been solvent debound. The dilatometric analysis showed that the specimen shrank in the early stage between 250 and 370 degreesC, not becau se of sintering, but through the loss of N, C, and O in the carbonyl iron p owder. At temperatures between 370 and 450 degreesC, the specimen expanded owing to the carburisation of the iron powder. The length change was also i nfluenced by the heating rate, debinding atmosphere, and the amount of the backbone binder. These dilatometric results are helpful in establishing the in designing binder compositions and schedules. guidelines debinding PM/08 98. (C) 2000 IoM Communications Ltd.