What is HIP?

Hot Isostatic Pressing, commonly abbreviated as HIP, is a supplementary procedure found within the spectrum of heat treatment techniques. It was developed to address the inherent challenges of porosity that often arise during various material manufacturing processes. Historically, the levels of porosity in cast materials have been predominantly influenced by the methodologies employed in foundries. The aim has been to mitigate the presence of gas molecules, particularly during the pouring stage and post-solidification, where shrinkage-induced issues manifest.

Furthermore, within the realm of powder metallurgy, the densification and sintering process is closely tied to the size of the powder used and other factors, including moisture content and lubrication within the powder. Consequently, when specifying the intended application, companies make deliberate selections of appropriate powders to diminish material porosity.

Hot Isostatic Pressing addresses these challenges by placing components in a chamber, heating them uniformly (typically up to 80-90% of the material’s melting point), and subjecting them to consistent pressure, reaching up to 207 MPa. For each type of material, temperatures, pressures and dwell times can be significantly changed, based on the process requirements. Typically, an inert gas like argon is used to prevent reactions with the components, ensuring a clean finish after the HIP process. The combined effect of heat and pressure leads to the material diffusing, effectively filling in microscopic gaps and diminishing voids within the component, resulting in a product, which has enhanced mechanical properties, such as fatigue resistance as an example, allowing high levels of performance at prolonged lengths of time. Additionally having predictable properties, allows design authorities to further improve designs and increase levels of safety significantly.