Powder metallurgy is the process of manufacturing parts using metal powders. Composites can also be generated by combining metal powder with nonmetals, commonly ceramic. This enables designers to achieve specific material properties in their parts.

One of the advantages of powder metallurgy is that it can produce complex shapes with minimal material waste and high precision. However, due to process limitations, powder-based manufactured parts are size and weight limited. Typically, they are under 2 inches in thickness and under 35 lbs per part.

General Powder Metallurgy Process

Generating metal powder involves reducing the size of metal pieces or ingots into fine particles by various methods, such as atomization, mechanical milling, or chemical reduction. The size, shape, and distribution of the metal powder affect the properties and performance of the final part.

Blending is the process of mixing different metal powders or adding nonmetallic additives to create a homogeneous mixture with the desired composition and characteristics. Blending can improve the strength, hardness, corrosion resistance, or wear resistance of the part.

Compacting is the process of applying pressure to the blended powder to form a coherent mass with a specific shape and size. Compacting can be done by using a die and a punch, a roller, or an isostatic press. The compacted powder is called a green part, which has low strength and density.

Sintering is the process of heating the green part to a temperature below the melting point of the metal powder, but high enough to cause diffusion and bonding between the particles. Sintering increases the strength and density of the part, as well as reduces porosity and improves dimensional stability.

Secondary Processes

The secondary processes typically used for powder metallurgy manufacturing are machining, sintering, heat treatment, and surface finishing. Machining is used to improve the dimensional accuracy and surface quality of the parts. Sintering is used to bond the metal particles together and increase the strength and density of the parts. Heat treatment is used to modify the mechanical properties and microstructure of the parts. Surface finishing is used to enhance the appearance, corrosion resistance, and wear resistance of the parts.

Other Powder Metal Methods

Isostatic Compaction

Isostatic compaction is a mass-conserving shaping process that applies uniform pressure on a powder mass in a flexible mold. The pressure can be applied by a fluid, such as water or oil, or by a gas, such as argon or nitrogen. Isostatic compaction can produce parts with high and uniform density, complex shapes, and fine details. Isostatic compaction can be performed at room temperature (cold isostatic pressing) or at elevated temperature (hot isostatic pressing).

Metal Injection Molding

Metal injection molding (MIM) is a metalworking process that combines the advantages of powder metallurgy and plastic injection molding. Finely-powdered metal is mixed with a binder material to create a feedstock that is then injected into a mold and solidified. The molded part is then removed from the mold and subjected to debinding and sintering processes to remove the binder and densify the metal particles. MIM can produce small, complex-shaped metal parts with outstanding mechanical properties, high accuracy, and excellent surface finish. MIM can use a variety of metals, such as stainless steel, titanium, copper, tungsten, and cobalt-chromium.