Engineering Reference

Precipitation hardening

Strengthening by forming fine particles of a second phase during a low-temperature ageing treatment.

Definition

The alloy is solution-treated and quenched soft, machined in that condition, then aged at a moderate temperature where fine precipitates form and raise the strength. Because the ageing temperature is low, distortion is minimal — which is the whole point.

17-4 PH and 15-5 PH are the common stainless grades; Inconel 718, Waspaloy and 13-8 Mo are high-temperature and high-strength examples. All of them machine in the soft condition.

Common misuse

Machining a precipitation-hardening alloy in the aged condition. It is dramatically harder and the part should have been finished before ageing.

Related