Powder Metallurgy is a continually and rapidly evolving technology embracing most metallic and alloy materials, and a wide variety of shapes. PM is a highly developed method of manufacturing reliable ferrous and non ferrous parts. The European Market alone has an annual turnover of over 12 Billion Euros, including ferrous, non ferrous, magnets, and hardmetals, with annual worldwide metal powder production exceeding 700’000 tonnes.
Created by mixing elemental or alloy powders and compacting the mixture in a die, the resultant shapes are then heated or “sintered” in a controlled atmosphere furnace to bond the particles metallurgically. The high precision forming capability of PM generates components with near net shape, intricate features and good dimensional precision pieces are often finished without the need of machining.
By producing parts with a homogeneous structure the PM process enables manufacturers to make products that are more consistent and predictable in their behaviour across a wide range of applications. In addition the PM Process has a high degree of flexibility allowing the tailoring of the physical characteristics of a product to suit your specific property and performance requirements. These include:
- Structural pieces with complex shapes
- Controlled Porosity
- Controlled performance
- Good performance in stress and absorbing of vibrations
- Special properties such as hardness and wear resistance
- Great precision and good surface finish
- Large series of pieces with narrow tolerances
The unique flexibility of the PM process enables products to be made from materials that are tailored to your specific needs. By using specially selected materials this capability enables refinements to be engineered into the mechanical properties of the part.
The growth of the P/M industry during the past few decades is largely attributable to the cost savings associated with net (or near-net) shape processing compared to other metalworking methods, such as casting or forging. In some cases, the conversion of a cast or wrought component to powder metal provides a cost savings of 40% or higher.
PM typically uses more than 97% of the starting raw material in the finished part and is specially suited to high volume components production requirements.
There are two principal reasons for using a powder metallurgy product:
- cost savings compared with alternative processes, and
- 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.
PM process enables products to be made that are capable of absorbing up to 35% of selected fluids.
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.
Raw material utilisation and energy requirements of various manufacturing processes.
This is a comparison between various manufacturing processes (Casting, Cold or Warm Extrusion, Hot Drop Forging, and Machining Processes) and PM sintering for a production of notch segments for truck transmission.
The PM process has:
- the highest raw material utilisation (over 95%)
- and the lowest energy requirement per Kg of finished part
- comparing with the other manufacturing processes
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. .
Comparison of the PM Process and Forging and Machining (energy requirements and number of process steps)
This is an example 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