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Q: I’m a PhD student in Malaysia, I would like to do research in “Material Processing – Development of Micro part using Metal Injection Moulding Process”. I would like to know new subjects in this field for research in the world.  Your guidance will be appreciated.

I would expect your Ph.D. supervisor to have the greatest say in this matter.  However here is my two cents:

As the parts become smaller in size, the powder also needs to be smaller in size to ensure the features you want to develop in the part are discernable.  With finer powder particles you need binders with molecular sizes comparable to your powders.

I hope this helps. I wish you luck with your studies.

Date asked: 24 November 2009

Q: We are looking for various powders for the welding industry. Do you have an insight into the welding industry and where we might be able to find potential reliable sources for our requirements?

This question is one for the welding industry.
 Please check out the following:
 The Welding Institute www.twi.co.uk
 Edison Welding Institute www.ewi.org
 American Welding Society www.aws.org

Date asked: 24 November 2009

Q: I wish to enter into the field of Iron powder manufacturing and seek your advise for the best possible manufacturing process. What would be the reduction process of sponge iron?

The “best possible manufacturing process” for making iron powder is a function of the application and how much of this application is being targeted.  The application determines the shape, size and size distribution of the particles required.

Iron powders can be made by:

• Reduction
  • Of ores including the Indian "blue dust"
  • Sponge Iron

• Atomization from a melt
  • Water atomization
  • Gas atomization

• Electrolysis

• Attrition

• Other chemical means
  • CVD
  • Dissociation of iron carbonyl

Although the specific application is not mentioned in the question, the largest volume of iron powder used in the powdered metal injection moulding industry today is made by the carbonyl process.

Date asked: 24 November 2009

Q: There has been a lot of talk on powder metal injection moulding of titanium but there seems to be very few parts being produced by this technology. Why?

Conventional powder metallurgy, the press and sinter technology, is a very accepted technology today and is used every day to produce hundreds of tons of parts.  We need to look into the history of powder metallurgy and go back about fifty years.  While powder metallurgy was know to be a viable technology, quality powders as we know today, specifications and the availability of different alloying elements were not so readily available and the industry was dependant on people with special qualifications and experience.  The powder metal injection moulding (MIM) technology is in a similar position today.  It is no longer a laboratory curiosity but an accepted technology for low alloy and stainless steels, while other “exotic” materials are making slow progress.

Titanium, because of its reactivity, has always been a difficult material to sinter, because once it reacts with carbon, nitrogen or oxygen it can not be reduced during the sintering process.  It also forms a stable hydride in hydrogen, which is difficult to reduce.  In case of MIM the finer powder used (d50 of about 22μm) adds to these problems.  The challenges are:

• Obtaining a powder with a sufficiently low oxygen content and maintaining the low oxygen level during processing.
• Using a secondary binder that dissociates without leaving carbon residues during the secondary debinding stage.
• Maintaining a clean furnace from which carbon and oxygen are not reabsorbed.
• The lack of specifications and the expectations that for all applications the specifications for wrought materials have to be met.
• The availability and cost of titanium powders.

Today there are a number of manufacturers that produce titanium alloy powders with low oxygen levels, including one that uses a plasma processing technology resulting in oxygen levels of around 100 ppm for MIM grade powders.  The cost is still an issue, but the use of novel technology for powder production to reduce costs is also making headway.

There are a number of binder systems available that leave almost no carbon residue and one major feedstock manufacturer is making CP titanium and Ti-6Al-4V feedstock.  Elnik Systems makes the only MIM furnace that allows for complete binder removal and sintering without adding oxygen or carbon using a partial pressure of argon for titanium based alloys.

Most manufacturers making MIM titanium parts are acting on their own.  When they come together to create new specifications for MIM titanium based alloys, the industry will grow faster.

Date asked: 24 November 2009

Q: I have one question regarding powder-metal products, its complexity to press, sinter and bringing it into final shape according to different specifications. Can you evaluate if MIM can substitute the before mentioned process? I have some market indications which tell me a new technology will and maybe can substitute the pressing/sintering/machining process.I would like to know your expertise.

Pressed and sintered parts that require extensive machining after sintering could be replaced by parts made by the powder metal injection moulding (MIM) technology. I could go on for pages comparing the two processes, but here are a couple of features that compare press and sintered parts with parts made by MIM that should pique your interest:

Press and Sinter Technology

1. Uniaxial pressing limits shape.
2. Densities of the parts are limited to about 92% maximum because of the powders used and the use of lower sintering temperatures. This results in poorer physical and mechanical properties.

Powder Metal Injection Moulding Technology

1. Injection moulding permits 3-dimensional features including internal and external threads. Parts made from multiple components may be replaced by a single component molded part.
2. Densities obtained are usually better than 96% and typically better than 98% with the porosity uniformly distributed. This results in physical and mechanical properties close to wrought products and better than cast products.

Costs are of course of prime importance when comparing processes, in which case the part would have to be redesigned to take advantage of the features of MIM. Rand German’s “Powder Injection Molding – Design and Applications” (published by Innovative Materials Solutions, Inc., State College, PA, 2003, ISBN 0-9727642-0-8) provides excellent insight to designing for MIM.

Date asked: 24 November 2009

Q: Can electrolytic iron powder be used for MIM. Are there any technologies that can be used to make it spherical?