Powder metallurgy and Isostatic Pressing
What is powder metallurgy?
Powder metallurgy is a metal-forming process performed by heating compacted metal powders to just below their melting points. Although the process has existed for more than 100 years, over the past quarter century it has become widely recognized as a superior way of producing high-quality parts for a variety of important applications. This success is due to the advantages the process offers over other metal forming technologies such as forging and metal casting, advantages in material utilization, shape complexity, near-net-shape dimensional control, among others. These, in turn, contribute to sustainability, making powder metallurgy a recognized green technology.
The most basic conventional powder metallurgy process, press-and-sinter, uses pressure and heat to form precision metal parts and shapes.
Other processes are also used to consolidate powders into finished shapes such as cold or hot isostatic pressing, direct powder rolling, forging, metal injection molding and gravity sintering.
Cold Isostatic Pressing
Cold isostatic pressing has the advantage for producing parts where the high initial cost of pressing dies cannot be justified or when very large or complex compacts are needed. A variety of powders can be pressed isostatically on a commercial scale, including metals, ceramics, plastics, and composites. Powders are compacted in elastomeric molds in either a wet or dry bag process.
Hot Isostatic Pressing
Hot isostatic pressing is a manufacturing process which utilizes elevated temperature and isostatic gas pressure to eliminate porosity and increase density in metals, ceramics, polymers, and composite materials. This improves the material's mechanical properties and potentially workability. Primary applications are the elimination of microshrinkage in castings, the consolidation of powders and diffusion bonding, often referred to as cladding. Hot isostatic pressing is also used as part of a sintering (powder metallurgy) process, for pressure-assisted brazing and for fabrication of metal matrix composites.
