1. A titanium industry for New Zealand?
Paul Ewart Ph.D (Candidate)
Professor Deliang Zhang Chief Supervisor
Undertaking PhD
Funded by UoW/ WaiCAM TRG, more recently Fulbright Fellowship Program and Trade & Industry
Powder metallurgy in support of a Titanium industry for NZ, big push and multi million dollar investments
Onekaka by Christine Whiteford
8 November 2018

2. Overview Introduction Titanium and its uses Titanium in New Zealand
Powder metallurgy
Metal injection moulding
The science of MIM
Google images
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8 November 2018

3. Introduction
The minerals rutile, anatase and brookite serve as a source for commercial Ti
The metal can also be mined from minerals such as ilmenite or leucoxene ores, or rutile beach sand
The biggest producers are Australia, India, Russia, South Africa and USA
Present ‘TiO2’. How it can be processed, adding value to NZ resources, being innovative.
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8 November 2018

4. Titanium and its uses
Ti and its alloys are used for bicycle parts to orthopaedic devices and spacecraft
They have superior corrosion resistance, strength and temperature performance
Negative aspects include high cost, poor machine-ability and a reactive nature
Materials properties, Strength 800 Mpa elongation 20%, alloyed 1200MPa+ 10%
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8 November 2018

5. Titanium in New Zealand
The use of Ti in NZ is limited to imported goods and some bar stock with use restricted because of high processing cost
NZ has its own resource, Titanomagnetite, the black iron sand of the West Coast
Used in steel production or sold unrefined
The Titanox process
Present ‘A titanium industry for New Zealand’ & ‘Ti from iron sand’.
How it can be processed, adding value to NZ resources, being innovative.
NZ industries:
Primary production of raw materials, wool, steel aluminium
Processing, agriculture, horticulture, forestry
Manufacturing, machining, fabrication, injection moulding
What is powder metallurgy???
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8 November 2018

6. Powder metallurgy
Powder metallurgy utilises the high surface energies of fine powders to process high temperature metals at reduced temperatures
Processing metal powders using press forming and sintering is limited to simple geometries
Metal Powder Injection Moulding (MIM) is a relatively new method of producing components with complex geometries
Present processing methods;
Cold compaction, Sintering
Cold compaction, Forging
Cold Compaction, Extrusion
Powder Extrusion
MIM/ TEx
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8 November 2018

7. Injection moulding
Injection moulding in New Zealand is a mature industry with many world leading companies
Equipment is produced in Europe, North America, China
MIM is a little known process in New Zealand
Why use MIM?
The moulding techniques developed for the plastics industry can be offered to MIM.
Complexity
MIM offers the same design freedom as plastic injection molding. The more geometrically complex a part is, the better suited to MIM process. Parts may include holes, threads, irregular shapes, splines, undercuts, grooves, complex contours, or cantilevers.
Parts that would usually be made by assembling multiple components can be designed as a single MIM part. Some parts that could not be fabricated via any other process can be made through MIM. Complexity that would be to costly with multiple machining operations or by casting and then finishing can be achieved cost effectively through MIM processing.
Size
Parts are within is 0.1 to 250 grams, above 100 grams the cost of the fine powders reduces cost advantages, unless the complexity is extreme. Wall thicknesses not less than .13 mm and not more than 12.7 mm. Material flow may limit the distance from gate to the farthest point on the part to around 100mm. Part tolerances are nominally ±0.3%–0.5%, although tighter tolerances can be achieved.
Production Volume
Medium to high volumes of 10,000 to 2,000,000 parts annually are needed to be able to offset tooling and start-up engineering costs. The best economic advantages are achieved at the highest quantities, due to the benefits of larger material purchases, multi-cavity tooling, and dedicated production units.
Final Properties
MIM fabrication is ideal where near-full density, high impact toughness, fracture toughness, and fatigue and corrosion resistance are required. And if non-standard material properties are required, these can be developed with new alloy systems.
MIM is appropriate for materials that are difficult to machine, have multi-phase microstructures, or high work-hardening materials. A high-quality surface finish and cleaner feature detail can be achieved than with investment casting.
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8 November 2018

8. Injection moulding process
Heat feedstock
Inject at pressure into closed mould
Cool and remove from mould
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8 November 2018

9. Metal injection moulding
Batching/ mixing
Compounding
Granulation
Injection moulding
Debinding
Sintering
Finishing
Metal powders have higher thermal conductivity, greater density and higher viscosity.
These differences must be taken into account when choosing the right machine, designing the mould and during processing.
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8 November 2018

10. Batching/ mixing Measuring correct ratio of metal powder to binder
eliminate agglomeration
dispersion of components
particle size distribution
Batching and mixing of the metal powder and binder components is in relation to a number of factors.
Batching:
The powder/ binder ratio must ensure the moulded shape is retained on removal from the mould.
30-50% is common
Physical limit imposed by particle shape and size 10-20% (fully dense)
Maintain encapsulation of the metal particles 20-30% (fully dense)
Mixing:
Eliminate agglomeration, Dispersion of components, Particle size distribution
Metal powders:
Particle shape, Irregular (flake, rod), Spheroid
Literature returns to the benefits of spherical powder, flow ability, packing
Size, less than 30um is considered better, <10um powders will give better mechanical properties but tends to create binder removal problems, 100um powders have been used and while they allow for faster debinding they
purity
Binder: Discussed in debinding section
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8 November 2018

11. Compounding
The batched and mixed powder feedstock is intensively mixed at elevated temperature to produce solid granular feedstock
Uniform rheological properties are essential for producing high quality parts
Compounding: mixing at elevated temperature which melts the binder
eliminate agglomeration
dispersion of components
particle size distribution
This produces a homogenous granular solid feedstock for injection moulding
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8 November 2018

12. Injection moulding
The feedstock is processed in the injection moulder at temperatures to enable uniform flow that fills the mould
This is the ‘Green Part’
To ensure efficient processing the temperature and pressure need to be optimised.
Temperature:
Titanium being high temperature is able to withstand C in air although it has been shown that impurity uptake into titanium will occur above 260C
Dependent on feedstock, especially binder
To enable flow of feedstock without reaction or degradation of either component
Equipment:
Barrel & Screw- conventional polymer processing equipment is okay, a need to use hardened surfaces to protect from hard alloys or
Mould- due to the binder in MIM feedstocks, cavities are designed ~20% larger than the final part size. Can have multiple cavities, inserts, slides, unscrewing cores, and hot runner systems.
The ‘Green Part’ needs to be strong enough to be handled/ transported to the next process
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8 November 2018

13. Debinding Thermal Solvent Catalytic
Following binder removal the part is called a ‘Brown Part’
The binder is removed to maintain purity of the required metal part and should not react with the metal powder the debound form is a ‘Brown part’.
Current research uses a number of different binders.
Polymer binder: PP, PE
Aqueous binder: PEG, Agar
Naphthalene:
Binder removal using:
Thermal degradation- Where the temperature is elevated to burn the polymer, this is okay for many metals but Titanium is susceptible to impurity uptake above 260C also residual carbon is left in the part, reportedly the amount is relative to the molecular weight of the polymer, hence use of lower MW polymer is better.
Catalytic decomposition- Polyacetals removed with acidic vapour catalyst
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8 November 2018

14. Sintering Held at ~1100C in inert atmosphere or a vacuum
Particles coalesce to form solid structure
Shrinkage is taken into account
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8 November 2018

15. Finishing HIP Minimal machining Internal threads Polishing
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8 November 2018

16. Automated MIM
With the advent of rapid binding technologies it should be possible to automate the MIM process with the use of robotic takeoff and computer controlled furnaces.
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8 November 2018

17. Quality of part
The optimum mechanical properties are possible but rely on essential operations to ensure best:
Green Part
Brown Part
Sintered Part
Finished Part
Particle surface morphology
Powder purity
[3] bulk or tap density, the form, the size distributions, the surface morphology, the specific surface area and flowability, and the moulding properties, all leading to an improved sintered product quality .
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8 November 2018

18. [1] Fabricating sports equipment components via powder metallurgy
[1] Fabricating sports equipment components via powder metallurgy. V S Moxson; F H Froes. JOM; Apr 2001; 53, 4
[2] The Metal Injection Molding Association, Princeton, New Jersey USA .
[3] Catamoldâ Feedstock for Powder Injection Molding: Processing - Properties – Applications. Technical Information, BASF Aktiengesellschaft 2002.
[4] Particle shape modification and related property improvements. Guosheng Gai, Powder Technology 183 (2008)
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8 November 2018

19. Question?
8 November 2018