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. During the process, if the compacted powders are prone to oxidation, nitrogen can be introduced to create an inert atmosphere. This helps prevent the oxidation of metal and ceramic powders, which is crucial for maintaining their chemical properties and performance.
Pressures required for compacting range from less than 5,000 psi to more than 100,000 psi (34.5 to 690 MPa). Powders are compacted in elastomeric molds in either a wet or dry bag process.
Hot isostatic pressing is a manufacturing process which utilizes elevated temperature and isostatic gas pressure to eliminat
e porosity and increase density in metals, ceramics, polymers, and composite materials. This improves the material's mechanical properties and potentially workability. Nitrogen is commonly used in hot isostatic pressing as a pressure-transmitting medium. As an inert gas, it can evenly transmit the isostatic pressure to the materials, facilitating the elimination of porosity and enhancement of density.
Primary applications are the elimination of microshrinkage in castings, the consolidation of powders and diffusion bonding, often referred to as cladding. During these processes, nitrogen also serves to create an inert atmosphere. This effectively prevents oxidation and other unwanted chemical reactions of the materials being processed, especially for metals and ceramics that are prone to oxidation at high temperatures. 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. In these applications, nitrogen helps maintain the chemical integrity and physical properties of the materials, ensuring the quality and performance of the final products.
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