Length Change and Deformation of Powder Injection-Molded Compacts during Solvent Debinding

摘要

Solvent debinding is one of the processes widelyadopted by the powder injection molding industry. Despite theinherent advantages of short debinding cycles, the lowtemperature employed, and the low investment in processingequipment, dimensional control is still a challenge to the furtherpromotion of this technology. The objective of this study was toinvestigate the causes of the tolerance-control problems bymeasuring the in-situ dimensional change and deformationbehavior of powder injection-molded (PIM) specimens duringdebinding, using a self-designed laser dilatometer. Swelling andsagging were found when compacts were immersed in thesolvent. Three major factors were found to be responsible forthe expansion of the specimens: dissolution of soluble binderinto the solvent, reaction between the insoluble binder andsolvent, and thermal expansion due to the temperature rise fromthe solvent bath. The amounts of expansion and sagging wererelated to the thickness of the sample, the amount of the binder,and the temperature employed. These in-situ measurements onthe dimensional change help explain how defects such asslumping, cracking, and distortion come about during debindingand provide some guidelines in selecting processing parametersand in designing binder compositions.