As in conventional PM,
powder forging begins with custom-blended metal powders being fed into a
die, then being compacted into a “green” shape, which is then
ejected from the die. This compact, called a “preform,” is different
from the shape the final part will acquire after being forged. Again as in
the conventional PM process, the green compact is sintered (solid-state
diffused) at a temperature below the melting point of the base metal in a
controlled atmosphere furnace, creating metallurgical bonds between the powder
particles and imparting mechanical strength to the preform.
The heated preform is withdrawn from the furnace, coated with a high-temperature
lubricant, and transferred to a forging press where it is close-die forged
(hot worked). Forging causes plastic flow, thus reshaping the preform to
its final configuration and densifying it, reducing its porosity to nearly
Powder forging produces parts that possess mechanical properties equal to
wrought materials. Since they’re made using a net-shape technology,
PF parts require only minor secondary machining and offer greater dimensional
precision and less flash than conventional precision forgings.
Parts fabricated through the PF process are subject to certain limitations.
Tooling and the maximum press tonnage capabilities impose size and shape
constraints on parts, just as in impression die hot forging. Annual production
quantities in excess of 25,000 pieces are typically required to amortize
the development costs of tool set-ups and maintenance. Finally, material
systems are somewhat limited (all commercial PF products are steel).
Typical Powder Forged Products—connecting rods, cams, bearing races,
Typical Markets Using Powder Forged Parts—automotive, truck, off-road
equipment, power tools