1. NZCCME 2013
Identification of Key Parameters for Injection Moulding Titanium Metals.
Ten minutes to present followed by five minutes to answer questions.
© Paul Ewart: November 2013

2. Introduction
Metal injection moulding (MIM) is an established manufacturing method.
Metal powders are mixed with a thermoplastic binder to form a feedstock that can be moulded to formed complex shapes (green parts).
The binder is removed (debinding) and the powders are consolidated (sintered) to form the final part with the desired metal composition.
© Paul Ewart: November 2013

3. Overview Research aims Binder Feedstock Moulding Debinding Sintering
Conclusion
© Paul Ewart: November 2013

4. Research aims
Investigate the selection of powder binding system for titanium metal.
Establish some relationships between debinding methods (solvent and thermal).
Determine effects of sintering on defect formation and metal composition of the parts.
© Paul Ewart: November 2013

5. Binder
Improve flow properties, promote particle dispersion and enhance wettability, and provide green strength
CW, LLDPE and PEG have been used successfully to produce titanium parts
© Paul Ewart: November 2013

6. Feedstock
TSE gave a uniform strand with residence time of five minutes
Interactions between components combined the thermal event temperatures
© Paul Ewart: November 2013

7. Moulding
Process temperature above all melting points and below the degradation points
Feedstock flow a function of fluidity of the binder
© Paul Ewart: November 2013

8. Thermal temp. (°C) duration (h)
Debinding
Solvent debinding
PEG8 through dissolution
Thermal debinding
CW and LLDPE through melt extraction, capillary action and (pyrolysis)
Residues removed early in sintering phase
Green Part #
Solvent duration (h)
Mass loss (%)
Thermal temp. (°C) duration (h)
Total mass loss (%)
Residue (%)
0.6 I 5
N/R
350
0.5
7.9
12.0 II 10
14.5
N/A
11.2
III 24 40
400 6
25.8
66.1
4.4
0.7
38.9
5.4
18.6
7.2 12
30.9
42.9
5.0 IV 27
48.2
75.7
2.1
© Paul Ewart: November 2013

9. Sintering One hour at 1250 °C
AIP molybdenum furnace with a static argon atmosphere
Mellen graphite furnace in a vacuum atmosphere (2.0 x 10-4 MPa)
Incomplete debinding ?
Furnace atmosphere ?
Something else ?
Powder loading between 0.6 and 0.7 would reduce distortion and blistering
© Paul Ewart: November 2013

10. Metal composition
Analysis to determine the relationship between the processing, the deficiencies and the final part
Density 91 % and 93 % for the argon and vacuum sinter respectively
© Paul Ewart: November 2013

11. Conclusion
Success with moulding does not ensure uniformity of the green parts
Combined solvent and thermal debinding enabled greater binder removal
The furnace conditions are critical and decomposition products must be removed to ensure they do not re-contaminate the parts.
© Paul Ewart: November 2013

12. Thank you. Questions please? Acknowledgements: NZCCME 2013
Funding from the University of Waikato doctoral research fund, WaiCAM and the Titanium research group.
Technical support from ProMould Custom Moulding, for producing the acetabular cup.
Analytical support from Titanium Development Association.
© Paul Ewart: November 2013