Hot isostatic pressing services apply high pressures and/or temperature to form near net shapes, densify parts, diffusion bond materials, remove internal porosity, and improve the integrity of engineered components. Hot isostatic pressing or HIP uses an argon atmosphere or other gas mixtures heated up to 3000º F and pressurized up to 100,000 psi. Typically, evacuated steel or metal cans or sintered surfaces are used to contain and maintain a seal during HIPing. Hot isostatic pressing services may specialize in applications such as densifying high-performance ceramics, ferrites and cemented carbides; net-shape forming of nickel-base superalloy and titanium powders; compacting of high-speed tool steel; diffusion bonding of similar and dissimilar materials; and eliminating voids in aerospace castings or creep-damaged blades.
Hot isostatic pressing services differ in terms of capabilities. Some companies specialize in canning or HIP tooling, casting densification, creep damage repair, densification or porosity removal, decanning or chemical milling, and diffusion bonding. Others specialize in graded compositions or transition joints, net or near-net shape fabrication, powder consolidation, powder preparation or blending, pressure brazing, and sinter HIP. Hot isostatic pressing services with equipment for experimental or pilot runs can assist in laboratory or developmental work such as process parameter studies, material development, or powder preparation samples. HIP services that provide production processing may also offer piggybacking, which allow the use of excess space within current production runs at a reduced cost. Piggybacking costs less than a dedicated run, but the experimental materials or parts in the small batch must be compatible with the materials and system for the large batch.
Specifications for hot isostatic pressing services include material processed and geographic regions served. Additional parameters cover operating pressure, operating temperature, and chamber dimensions. The operating pressure is the maximum operating pressure required to reach the desired density during part production. The required pressure varies with material and part geometry. Similarly, operating temperature is the maximum operating temperature developed within the press during compaction. This specification applies to both hot isostatic pressing services and hot uniaxial pressing services. The internal diameter of the HIP chamber determines the maximum diameter or width capacity. Allowance must also be made for elastomeric or steel can tool wall thickness, however.