A cold pressed detail of powder, so-called green body, is fragile and easily damaged. To achieve the required strength the green body must be burned (sintered) under protective atmosphere without air. The powder grains merge and the alloying elements dissolve.

The part can be pressed and sintered, one or more additional times to achieve better dimensional accuracy and strength. It can also be hardened as ordinary steel to obtain the desired properties.

Ref. Steel and its Heat Treatment – A Handbook (6.4.1)