Hot isostatic pressing

The Hot isostatic pressing process (HIP) is to load the powder compact or the powder packed into the sheath into a high-pressure container, so that the powder can be subjected to high temperature and balanced pressure, and then sintered into a dense part. The Hot isostatic pressing technology was first developed by the Battelle Columbus laboratory in 1955. The basic principle is that gas is used as the pressure medium, and inert gases such as helium and argon are usually used. The material (powder, billet or sintered body) undergoes anisotropic pressure during the heating process, and the combined effect of high temperature and high pressure promotes the densification of the material. The HIP process was first applied in the preparation of hard alloys, mainly for the treatment of castings. After nearly 50 years of development, its application scope in industrial production has been continuously expanded. In the past 10 years, by improving Hot isostatic pressing equipment, the production cost has been greatly reduced, and the application scope of Hot isostatic pressing technology in industrial production has been widened, and its application scope still has great potential. At present, the main applications of Hot isostatic pressing technology include: consolidation of metals and ceramics, sintering of diamond tools, repair and improvement of casting quality, densification of high-performance magnetic materials and t

argets.

Compared with the traditional pressureless sintering or hot pressing sintering process, the Hot isostatic pressing process has many outstanding advantages:

① By using HIP sintering, the densification of ceramic materials can be achieved at much lower temperatures than pressureless sintering or hot pressing sintering, which can effectively suppress many adverse reactions or changes in the material at high temperatures, such as abnormal grain growth and high-temperature decomposition; Materials that cannot be sintered under normal pressure may be sintered. As for alumina ceramics, ordinary sintering must reach a high temperature above 1800 ℃ under normal pressure, while hot pressing (20MPa) sintering needs to reach around 15000 ℃, while HIP (400MPa) sintering has already densified at a lower temperature of around 1000 ℃;

② By using the HIP sintering process, dense ceramic sintered bodies with uniform microstructure and almost no pores can be prepared with reduced or even no sintering additives, significantly improving the various properties of the material;

③ Through the HIP post-treatment process, residual pores in the sintered body can be reduced or even eliminated, surface cracks can be healed, and the density and strength of ceramic materials can be improved;

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