There are two principal reasons for using a powder metallurgy product:

• (1) cost savings compared with alternative processes, and
• (2) unique properties attainable only by the PM route.

In the automotive sector, which consumes about 80% of structural PM part production, the reason for choosing PM is, in the majority of cases, an economic one.

Why then is PM more cost effective?

BETTER MATERIAL UTILISATION WITH CLOSE DIMENSIONAL TOLERANCES.Conventional metal forming or shaping processes, against which PM competes, generally involve significant machining operations from bar stock or from forged or cast blanks.

These machining operations can be costly and are wasteful of material and energy.

This is illustrated in the figure below which shows that material utilisation in excess of 95% can be achieved with close dimensional tolerances.

ENERGY SAVINGS. The energy savings alone contribute significantly to the economic advantage offered by PM.

• An example is given below for a notch segment used in a truck transmission, where PM consumes only around 43% of the energy compared with forging and machining and the number of process steps has been greatly reduced.

MACHINING COSTS. There are applications where in-house machining is carried by the automotive customer on high capital cost plant, and the fixed costs (and particularly the required return on capital investment) dominate the total cost of machining.

In such cases, the PM product sometimes shows a cost advantage only when these full machining costs are considered.

The case of PM connecting rods is an excellent example of such an application.