All of the above answers are correct, but the method you use depends entirely on what metal you are working with and how you want to use the powder afterwards. For instance, water atomisation works for iron powders as iron can be easily melted - it does not work for tungsten which has a high melting temperature; it produces iron powders that are irregular in shape - perfect for die compaction, disaster for powder injection moulding. Or producing powders by a chemical reduction route can produce fine powders, but their contamination level from the precursor salts can result in poor material quality after sintering. So, your question needs to be fully stated for a useful answer to be supplied.

One of the adopted practice is to to melt the bulk metal preferably by induction furnace. The liquid metal is dropped from a height in a protected chamber when these liquid metals are impinged by high pressure water jet which atomise the liquid metal into very fine particles. These collected particles with water are dried and can be sieved through a vibrator to assort particles of different mesh sizes.

The four common methods used to produce metal powders are

Solid state reduction by crushing normally used for iron powder,

Atomisation, - can be used for all metals and alloys with the assistance of a gas or the help of a rotating disk.

Chemical, and

Electrolysis - by using a spinning consumable electrode like in the case of a Manual Metal Arc Welding.

Atomisation by a rotating disc is easy and cheaper but tends to casue large virabtion/loud noise and cannot very fine powders.

Gas atomisation can produce finer powders but is more costly.

We have made metal powders by electrochemical reduction of the respective metal oxide powders (packed) in molten salts. This method is known as the FFC Cambridge Process, and it is particularly suitable for making refractory metal powders (Ti, Zr, Nb, Ta, Mo, W, Cr, ....).

I do not know which metals you are working on, but several metals become brittle when they are annealed in H2. Once they are brittle, it is easy to crush/mill them into powders.

All of the above answers are correct, but the method you use depends entirely on what metal you are working with and how you want to use the powder afterwards. For instance, water atomisation works for iron powders as iron can be easily melted - it does not work for tungsten which has a high melting temperature; it produces iron powders that are irregular in shape - perfect for die compaction, disaster for powder injection moulding. Or producing powders by a chemical reduction route can produce fine powders, but their contamination level from the precursor salts can result in poor material quality after sintering. So, your question needs to be fully stated for a useful answer to be supplied.

The answer will also depend on the quantities involved. I use a planetary ball mill with zirconia grinding balls and jars to quickly and simply powder metallic, intermetallic and ceramic castings for X-ray diffraction. The only drawback is the possibility of contamination with ZrO2. Clearly though, this method is not ideal for industrial scale use!

Dear Jiambo,

I think that you should precise something more in your question, particularly the kind of "bulk metal". It is reactive or not ? What is his melting temperature? What size of final powders you are looking for? Your "bulk metal" is brittle or ductile? What is the amount of powders you are looking for, grams, kilograms or tons?

The best potential technique to be used depends on the answers you give to such questions (and others). So in what follow I answer you in a general way.

For bulk metals the most useful techniques to obtain relatively fine powders are water atomization and gas atomization. The former is industrially cheaper than the second one, but water atomization produces irregular powders of a relatively big size (above some hundred of micrometers) and in addition the reactivity of water with melted metals is usually high and the final powders contain a lot of oxide particles embeded into the powders.

If you require to obtain "clean" metal powders with small size (below 100 micrometers) you should use gas atomization. This technique can work even for high melting point metals, because at present there are levitation induction furnaces coupled to the atomizers. This is a conceptually simple method: melting and atomize; but obviosly in not low cost and you cannot find the equipment easily. However if you are not looking for an industrial process with big amount of powders, but rather you are dealing with a research work, I recommend to contact with some research laboratory having such equipment and ask for collaboration, if your material looks interesting the answer probably will be positive. Usually with one atomization you will have several kilograms of good powders, which will be well enough for a good research project.

Please let us know more details if you require a more precise answer.

Good luck with your powders.

Thank you for all of the attention. I would like to make my powers with gas atomization because of the high melt point and the good quality required by the use afterwards. I want to prepare metal matrix composites with this power.