Infiltration

Where it comes up

• Powdered metalNet-shape gears, bushings, and structural parts pressed from metal powder and sintered, with little or no machining.

Related terms

Sintering

Sintering is heating compacted metal powder below its melting point, typically around 2,050 °F (1,120 °C) for iron-based parts, in a controlled atmosphere so the particles bond metallurgically. It turns a fragile green part into a strong, finished component. Parts may then be sized, machined, or heat treated.

Porosity

Porosity is voids inside a cast or sintered part, caused by trapped gas or by shrinkage as metal solidifies. In die castings it can cause leaks and weaken machined surfaces. It is controlled with gating, venting, and vacuum assist, and pressure-tight parts are sealed by vacuum impregnation.

Green part

A green part is a powder metal part after compaction and before sintering. It holds its shape but has low strength, about like chalk, so it must be handled carefully. Green density, typically 6.4–7.2 g/cm³ for iron-based parts, sets final strength after sintering.