What is Powder Metallurgy? – Definition, and Process

What Is Powder Metallurgy?

Powder metallurgy is a term covering a wide range of ways in which materials or components are made from metal powders. This process can avoid, or greatly reduce, the need to use metal removal processes, thereby drastically reducing yield losses in manufacture and often resulting in lower costs.

Powder metallurgy is a metal forming process in which compacted metal powders are heated to just below their melting point. Although the process has been around for more than 100 years, over the past quarter-century it has been widely recognized as a superior method for making high-quality parts for a variety of important applications.

This success is due, among other things, to the advantages that the process offers over other forming technologies such as forging and metal casting, advantages in material use, the complexity of the shape, and the control of the shape in the vicinity of the network shape. These in turn contribute to sustainability and make powder metallurgy a recognized green technology.

Powder Metallurgy Process

These production technologies generally involve all or most of the following process steps:

  • Production of Metal Powder
  • Mixing and Blending
  • Compaction and shaping of the powder
  • Sintering of the compact to enhance integrity and strength
Powder Metallurgy Process

Sometimes, this process accomplished with some secondary operations like sizing, coining, infiltration, hot forging, etc.

1. Powder production

Almost all iron powders for the production of PM components are produced either using the sponge iron process or by water atomization. Non-ferrous metal powders used for other PM applications can be made by a number of processes.

2. Mixing of powders

This can often include the incorporation of alloy additives in the form of an elemental powder or the incorporation of a press lubricant.

3. Forming of the mixed powder into a compact

The dominant consolidation process involves the press-fitting of a rigid tool set that includes a die, punches, and possibly mandrels or core rods. However, there are several other consolidation processes that are used in niche applications.

4. Sintering of the compact to enhance integrity and strength

This process step involves heating the material, usually in a protective atmosphere, to a temperature that is below the melting point of the major constituent.

In some cases, a minor constituent can form a liquid phase at sintering temperature; such cases are described as liquid phase sintering. The mechanisms involved in the solid phase and liquid phase sintering are discussed briefly in a later section.

5. Secondary operations

The application of finishing processes to the sintered part. In powder metallurgy, such processes are often referred to as “secondary operations”.

Advantages of the powder metallurgy process

  • Minimizes machining by producing parts at or near-final dimensions
  • Minimizes scrap losses by typically using more than 97% of the raw material in the finished part
  • Allows a variety of alloy systems
  • Produces a good surface quality
  • Provides materials that can be heat-treated to increase strength or wear resistance
  • Provides controlled porosity for self-lubrication or filtration
  • Facilitates the creation of complex or unique shapes that would be impractical or impossible with other metalworking processes
  • Is suitable for the production of medium to high volume components
  • Provides long-term performance reliability in critical applications
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