Precipitation Hardening Steel {17-4 PH} & It's Heat Treatment

Precipitates are small particle phases; for example, in the case of 17-4 PH steel, it's copper.

These particles are scattered throughout the steel, making it harder for the steel to deform and thus increasing its hardness and strength.

Precipitation hardening is a type of steel that becomes drastically stronger and harder through a specialized heat treatment process called age hardening.

The ageing(holding steel at a lower temperature) process causes the copper atoms to cluster together and form copper-rich precipitates.

When metal is cooled fast in solution annealing, the precipitation temperature is bypassed, which doesn't allow copper precipitates to form and thus results in a soft metal.

This shows the specialty of precipitation hardening steel, which completely transforms its mechanical characteristics after the ageing process. These types of steel are therefore used in aerospace applications requiring super tough and strong components (after age hardening) and also precision machining at a softer state(solution annealed).