Rapid debinding of 316L stainless steel injection moulded component

Wax-based binder system is widely used but they suffer from long debinding time and a tendency to slump or distort during debinding. This has been a major obstacle for the economic process for metal injection moulding (MIM). For improving the debinding process, two-step debinding process has been introduced. Gas-atomised 316L stainless steel powder was injection moulded using two types of multi-component binder system comprising (1) a major fraction of paraffin wax and a minor fraction of polyethylene (PE) and stearic acid (SA) as a lubricant, (2) a major fraction of polyethylene glycol (PEG) and a minor fraction of polymethyl methacrylate (PMMA) binder system. Debinding was carried out in two steps; first, the moulded part is immersed in heptane or distilled water at 60 °C to remove the major component of the binder and then heated to remove the remaining binder. The results show that no swelling or distortion was observed on the moulded specimens on both binder systems. Furthermore, the specimens had an adequate strength for handling even after solvent extraction. Large pore were formed from the surface to the interior of the debound part during solvent extraction, allowed easy escape of pyrolysis gases during thermal debinding. Thermal debinding with ramp heating at rates from 3 to 15 °C/min was found to be successful.