Hot pressing is one of the fabrication techniques in which metals, alloys or ceramics powders are consolidated under simultaneous heat and pressure to form a monolithic component. This forming process is used to reduce the metals porosity and increase the density of many ceramics. It also improves the mechanical properties and workability of powder materials. This process is one of the most important processes used in powder metallurgy.
In this process, a suitable mold (typically steel or graphite) is designed, and the powder materials with desired chemical composition are prepared. Then, the powder is poured into the mold and placed inside the chamber. By applying heat and pressure simultaneously to the mold, the diffusion processes are activated. Depending on the applied pressure and temperature, different phenomena such as particles displacement, plastic deformation or creep can occur at the particles interface; these phenomena all contribute to the consolidation of particles.
In this process, because of applying a relatively uniform pressure in all directions, the final structure is without porosity and the component final properties are isotropic. Due to the application of high pressures (100 to 200 MPa), use of high strength alloys in fabrication of the device chamber is necessary. Furthermore, based on the powder type, the temperature varies from 900 to 1250 oC.
In this process, an induction system is typically used to create heat inside the mold which can increase the temperature up to 1500 oC in a time less than 90 seconds. It is noticeable that in this process all parameters such as pressure, temperature, time, component dimensions and density are controllable. The main parts of a hot pressing machine include vacuum and gas system, hydraulic system, induction heating system, water cooling system, monitoring and control system. The parts manufactured with this method include a wide range of materials. It is also possible to produce components with different dimensions; some of these are large parts used in the oil industry, turbine blades, and small parts used in machining tools and drilling.
Vacuum Hot pressing machine, supplied by manufacturer, provides the ability to fabricate dense components under high vacuum, temperature and pressure. Furthermore, development of new materials with certain special features such as amorphous phases, reduced materials gap, high strength and even specific changes in materials structure can be done. Details of technical specifications are presented in the following Table.
Hot pressing technique is one of the main processes in manufacturing of ceramic, composite and even powder metallurgy components. In this forming method, by applying simultaneous heat and pressure, fabrication of high density parts is possible. Therefore, by using nanoscale objects, nanocomposite parts with high quality and high strength can be produced.