Removal of Paraffin Wax Binder from Metal Injection Molded Part by Supercritical Fluids

Abstract

The metal injection mold (MIM) process is the most cost effective, highest quality means to produce complex shaped, high performance parts. In the MIM process, debinding is a key step for successful MIM. However, the conventional debinding processes, which are thermal debinding and solvent debinding, have disadvantages that include long product development times, and harm to the environment. Therefore, the study of supercritical CO₂ that can be used as solvent for debinding, a new debinding technology as substitute for a conventional technology, was considered. In this paper, we used two methods to investigate a method for reducing debinding time as well as lowering operation condition other than pure supercritical CO₂ debinding: the first method was to add cosolvent in supercritical CO₂, the second method was to use the mixture of propane + CO₂, as the supercritical solvent. It was found that the addition of cosolvents and the use of binary mixture propane + CO₂ for supercritical solvent remarkably improved the binder removal rate, in comparison with using pure supercritical CO₂.

Keywords:

• Supercritical CO₂ debinding
• Wicking debinding
• Metal injection molding
• Cosolvent
• Propane

Acknowledgment

This work was supported by Ministry of Science and Technology of Korea, and the National Research Laboratory Program for Supercritical Fluid. The financial contribution is greatly appreciated.