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Development of the 2-Component-Injection Moulding for Metal Powders
von Ana Paula Cysne Barbosa2-Component-Metal Injection Moulding (2-C-MIM) is a technique derived from plastics
industry which has been adapted to metal powders. By using this technology, the production
of titanium parts combining dense and porous parts becomes possible. Such a structure with a
gradient in porosity is attractive for biomedical implants, as the pores promote a mechanical
interlock between bone tissue and implant material. The dense part of the structure is
responsible for the mechanical stability of the implant.
For the fabrication of metal parts with a gradient in porosity, feedstocks with and without
space holder particles are employed. A 2-C-MIM machine and a specifically designed tool are
used for the combination of these feedstocks in the same green part. After removal of the
binder and space holder material, the parts are sintered and a structure with a gradient in
porosity is obtained.
First 2-C-MIM experiments were conducted with a standard binder system previously
developed at the institute IEK-1 at Forschungszentrum Jülich. Results achieved with this
binder system indicated binder-powder phase separation during injection, which occurred due
to the low viscosity of the binder system used (0.15 Pa·s). The need for the development of a
new binder system with a more suitable flowing behaviour became clear. Moreover, the
partial debinding method employed so far (wicking) needed to be substituted by another
method with a more industrial approach.
New binder systems comprising a wide range of viscosity were developed, where the partial
debinding method employed was solvent extraction in n-hexane. A binder system with a
viscosity of 12.4 Pa·s was chosen for further investigations, due to the suitability of flowing
behaviour of its feedstock. The viscosity of feedstocks was measured, where the use of space
holder particles was found to decrease viscosity. After addition of stearic acid and
optimisation of the solids content, feedstocks with 72 and 64 Vol.% solids loading (with and
without space holder, respectively) were used in injection moulding trials.
After optimisation of the injection temperature of feedstock, prototypes of titanium spinal
implants with a gradient in porosity were successfully produced and characterised. The
availability of the net-shape production of such implants by 2-C-MIM means a reduction of
costs in case of large scale production, as compared to the fabrication method current
employed (pressing and green machining).
industry which has been adapted to metal powders. By using this technology, the production
of titanium parts combining dense and porous parts becomes possible. Such a structure with a
gradient in porosity is attractive for biomedical implants, as the pores promote a mechanical
interlock between bone tissue and implant material. The dense part of the structure is
responsible for the mechanical stability of the implant.
For the fabrication of metal parts with a gradient in porosity, feedstocks with and without
space holder particles are employed. A 2-C-MIM machine and a specifically designed tool are
used for the combination of these feedstocks in the same green part. After removal of the
binder and space holder material, the parts are sintered and a structure with a gradient in
porosity is obtained.
First 2-C-MIM experiments were conducted with a standard binder system previously
developed at the institute IEK-1 at Forschungszentrum Jülich. Results achieved with this
binder system indicated binder-powder phase separation during injection, which occurred due
to the low viscosity of the binder system used (0.15 Pa·s). The need for the development of a
new binder system with a more suitable flowing behaviour became clear. Moreover, the
partial debinding method employed so far (wicking) needed to be substituted by another
method with a more industrial approach.
New binder systems comprising a wide range of viscosity were developed, where the partial
debinding method employed was solvent extraction in n-hexane. A binder system with a
viscosity of 12.4 Pa·s was chosen for further investigations, due to the suitability of flowing
behaviour of its feedstock. The viscosity of feedstocks was measured, where the use of space
holder particles was found to decrease viscosity. After addition of stearic acid and
optimisation of the solids content, feedstocks with 72 and 64 Vol.% solids loading (with and
without space holder, respectively) were used in injection moulding trials.
After optimisation of the injection temperature of feedstock, prototypes of titanium spinal
implants with a gradient in porosity were successfully produced and characterised. The
availability of the net-shape production of such implants by 2-C-MIM means a reduction of
costs in case of large scale production, as compared to the fabrication method current
employed (pressing and green machining).