The greatest advantage to Powdered Metal processes is that the need to use metal removal processes can be avoided, or greatly reduced, thereby drastically reducing yield losses in manufacture often resulting in lower costs. Various parts that can be costly and time consuming to manufacture such as metal gears, or parts that require square holes can be manufactured in less time and are cost efficient if done by a powdered metallurgy process.
Sintering is a heat treatment applied to a powder compact in order to impart strength and integrity. The temperature used for sintering is below the melting point of the major constituent of the powder metallurgy material. After compaction, neighboring powder particles are held together by cold welds, which give the compact sufficient “green strength” to be handled. At sintering temperature, diffusion processes cause necks to form and grow at these contact points.
There are two necessary precursors before this “solid state sintering” mechanism can take place:
- Removal of the pressing lubricant by evaporation and burning of the vapors
- Reduction of the surface oxides from the powder particles in the compact.
These steps and the sintering process itself are generally achieved in a single, continuous furnace by judicious choice and zoning of the furnace atmosphere and by using an appropriate temperature profile throughout the furnace.
The process of sintering has many advantages. Those advantages include:
- Very high levels of purity and uniformity in starting materials.
- Preservation of purity, due to the simpler subsequent fabrication process (fewer steps) that it makes possible.
- Stabilization of the details of repetitive operations, by control of grain size during the input stages.
- Absence of binding contact between segregated powder particles – or "inclusions" (called stringering) – as often occurs in melting processes.
- No deformation needed to produce directional elongation of grains.
- Capability to produce materials of controlled, uniform porosity.
- Capability to produce nearly net-shaped objects.
- Capability to produce materials which cannot be produced by any other technology.
- Capability to fabricate high-strength material like turbine blades.
- After sintering the mechanical strength to handling becomes higher.
Almost any substance can be obtained in powder form, through either chemical, mechanical or physical processes, essentially allowing material to be obtained through sintering. When pure elements are sintered, the leftover powder is still pure, so it can be recycled.
The process of sintering a metal is very cost effective for parts that can be fabricated using this method. There is virtually no wasted material and the labor content is very low. The one-time tooling cost is moderate, but will often produce millions of pieces. AMFAS can provide the best value solutions for any components that are suitable for powdered metal production.