Metal powders are finely divided or powdered metals used in fabricating sintered parts, thermal spraying, filling plastics, and other specialized applications. Powdered metals include most types of metals.

Metal powders are used in powder metallurgy, which is the process of making metal parts and components by heating compacted powdered metals to just below melting. Powder metallurgy is also known as press-and-sinter. Many metals are treated with this process to produce a porous material called sponge fines. For example, iron sponge fines are small particles of iron ore that have been reduced by heat. Sponge iron can come in lumps or finer particles and is frequently used as an alternative to steel scrap metal.

The advantages to using this method to create metal parts include elimination of much of the waste of traditional machining, the ability to create a wide variety of alloyed components, and the ability to heat-treat materials for increased strength.

Making Metal Powders

Metal powders are made using a variety of techniques. Powdered metal can be milled, atomized, precipitated, or blended to proper consistency and texture for a specific use.

• Milled metal powders are made through a milling machine which physically grinds the metals to a powder form. Milling is not generally used for metals that are combustible in powder form.
• Atomized metal powders are made by separating molten metal into small droplets that are then frozen solid.
• Precipitated metal powders are high in purity and can be made in precise particle sizes. Some metal powder is made through electrolysis resulting in high-purity, high-density powder made of copper and magnesium.
• Blended, or mechanically alloyed metal powders are mixtures of powders that are crystallized at atomic levels, forming a compound with uniformly dispersed particles, ensuring the final product’s high strength.

Many other metal powders are pre-alloyed, meaning that every particle in the powder mixture contains more than one element. Metal powders are used to make all kinds of metal parts, and are also used in sintering applications, polyester fiber spinning, injection molding, and brazing.

Selection Criteria

When selecting metal powders, there are a number of factors to consider. The most important factor is the metal or alloy type and should be selected based on the service conditions of the end product being manufactured. Other criteria include the powder’s mechanical properties such as tensile strength and yield strength, important for determining how the material will act under stress in application.

For more detailed information on individual types of metals, please visit either of Engineering360’s Specification Guides on metals (“Nonferrous Metals and Alloys” or “Ferrous Metals and Alloys”) or search for a specific metal or alloy of interest.

Applications

Metal powders are used in a number of applications including:

• Chemical processes
• Food supplements and additions
• Friction materials
• Magnetic composites
• Polymer filtration
• Printing
• Surface coatings
• Welding

Image credit:

Belmont Metals, Inc.