Metal powders can be made several ways, but atomisation dominates modern supply because it gives close control over particle size, shape and purity. Knowing how gas and water atomisation differ helps buyers match a powder to the process that will consume it.

How atomisation works

Atomisation converts a molten metal stream into fine droplets that solidify into powder. Liquid metal is poured through a nozzle, where a high energy fluid jet strikes the falling stream and breaks it into droplets. Surface tension pulls each droplet toward a sphere, while the cooling rate decides how far that happens before the metal freezes. The choice of atomising fluid, gas or water, sets the cooling rate and, with it, most of the powder properties that matter downstream.

Gas atomisation

In gas atomisation an inert gas, typically nitrogen or argon, forms the disrupting jet. Cooling is comparatively slow, so droplets have time to relax into near spherical shapes before solidifying. The inert atmosphere keeps oxygen pickup low, commonly below a few hundred parts per million for many alloys. The result is a clean, spherical, free flowing powder that packs and spreads consistently. These traits make gas atomised powder the standard feedstock for metal additive manufacturing, metal injection moulding and thermal spray, where flowability and packing density govern part quality.

Water atomisation

Water atomisation replaces the gas jet with high pressure water. The far faster quench freezes droplets before they can round off, producing irregular, ligamental particles with a rougher surface. Rapid cooling and contact with water raise oxygen content relative to gas atomised powder, so an anneal or reduction step is often applied. The irregular shape is not a defect. Interlocking particles give the green strength needed to hold a shape after pressing, which is why water atomised powder is the workhorse of press and sinter parts, friction materials and many chemical and metallurgical uses. Water atomisation is also more economical at scale.

Controlling particle size and distribution

Particle size is tuned mainly through fluid pressure and flow, melt superheat, nozzle geometry and the metal feed rate. Higher jet energy shears the stream into finer droplets, giving a smaller median size. Producers then classify the powder by sieving, air classification or cyclone separation to hit a target distribution, for example a narrow cut for additive manufacturing or a broader spread for good packing in compaction. Because size, shape and oxygen move together, powder is specified against the receiving process rather than optimised in isolation.

Matching route to application

Choose gas atomised spherical powder when flow, high packing density and low oxygen are decisive, as in additive manufacturing, metal injection moulding and thermal spray. Choose water atomised irregular powder when green strength and cost per kilogram lead, as in conventional press and sinter compaction. Many copper, tin, bronze and iron based powders are available by either route, so the deciding factor is usually the process, not the metal.

  • Particle shape: Gas atomised: Spherical; Water atomised: Irregular
  • Typical size range: Gas atomised: 10-150 microns; Water atomised: 20-200 microns
  • Oxygen content: Gas atomised: Lower; Water atomised: Higher
  • Flowability: Gas atomised: Excellent; Water atomised: Moderate
  • Typical use: Gas atomised: Additive manufacturing, MIM; Water atomised: Press and sinter compaction

Key takeaways

  • Gas atomisation yields spherical, low oxygen, free flowing powder ideal for additive manufacturing and injection moulding.
  • Water atomisation yields irregular, higher oxygen powder with the green strength suited to press and sinter compaction.
  • Particle size is controlled through jet energy, melt temperature, nozzle design and feed rate, then refined by classification.
  • Specify powder against the downstream process, since shape, size, oxygen and flow are linked.

Supplying metal powders since 1945 and certified to ISO 9001 and ISO 14001, Ronald Britton can help you select the right atomisation route to specification and dispatch from UK stock within 48 hours. Request a quote or contact our technical team to discuss your particle size, shape and purity requirements.