Hot Isostatic Pressing
A process for eliminating internal pores and defects through the simultaneous application of high temperature and omnidirectional gaseous pressure on the component. This drastically increases the integrity and ductility of the microstructure.
HIP is a post-treatment process that densifies components under heat and all-around gas pressure. It smooths out internal pores and voids from welding or casting, making the structure denser and tougher. You run the part in a pressure chamber where it's uniformly compressed from all sides while hot. The material must be clean and tight, otherwise the whole procedure is useless – and if you don't control the parameters, the material gets worse rather than better. Basically, HIP is the last resort to salvage a porous part before scrapping it.