A comparison of titanium MIM parts produced using various furnace conditions. © Paul Ewart:...

A comparison of titanium MIM parts produced using various

furnace conditions.

© Paul Ewart: December 2013

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

Overview

Research aims

Feedstock

Moulding

Debinding

Sintering

Conclusion


Research aims

• To investigate impurity uptake in relation to sinter conditions

• To define defect formation with respect to metal composition within sintered parts



Feedstock

Binder combination of bees wax (BW), carnauba wax (CW), linear low density polyethylene (LLDPE), polyethylene glycol (PEG) and polypropylene (PP)

The powder was titanium alloy (Ti-6Al-4V of 200 mesh, HDH)

Moulding

Process temperature above all melting points and below the degradation points

Feedstock flow a function of fluidity of the binder


Debinding

Solvent debinding targeted PEG with dissolution

Thermal debinding targeted waxes by melt extraction, capillary pressure and volatilities

Polyolefins and remaining residues removed early in sintering phase by pyrolysis @ < 93 %


Image Furnace Temperature

(°C) Hold time

(Min) Atmosphere Pressure (MPa)

a Molybdenum 1250 60 Static argon Atm b Vacuum 1250 180 Vacuum 2.0 x 10-4

c MIM vacuum 1350 180 Argon flow/ Vacuum 2.0 x 10-3

Sintering


Incomplete debinding ?

Furnace atmosphere ?

Through part ?

External surfaces do not necessarily represent the metal composition of the part

Micro-structure analysis to investigate residual binder levels, elemental diffusion and density

Density 91, 93 and 96 % respectively

Metal composition


Conclusion

Static atmosphere produced the highest level of impurities

Vacuum sintering removed more residue but impurities remain from pore disconnection

Sweep gas during heat-up enhanced residue removal and with vacuum atmosphere impurities were reduced.


Thank you.Questions please?

Acknowledgements:Aamir Mukhtar and the Titanium Industry Development Association (TiDA), Tauranga, NZ for analytical support.ProMould Custom Moulding Ltd, Hamilton, NZ for part moulding.AME Powder Technology Limited, Hamilton, NZ for sample preparation and sintering assistance.


A comparison of titanium MIM parts produced using various furnace conditions. © Paul Ewart:...

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