Powder metallurgy is a highly developed method of manufacturing reliable ferrous and nonferrous parts by forming and sintering metal powder. Powder metallurgy is similar to the production of ceramics. Therefore, a series of new powder metallurgy technologies can also be used for the preparation of ceramic materials. Because of the advantages of powder metallurgy technology, it has become the key to solve the problem of new materials and plays an important role in the development of new materials.
There are many factors affecting the properties of sintering, the main is the properties of the powder, the forming conditions and the sintering conditions. The factors of sintering conditions include heating rate, sintering temperature and time, cooling rate, sintering atmosphere and sintering pressure, etc..
(1) Sintering temperature and time
The sintering temperature and time influence the porosity, density, strength and hardness of the sinter. When sintering temperature is too high and time is too long, the performance will be degraded, or even there will be over-burning flaw. The sintering temperature is too low or time is too short, and the performance will be degraded due to under-burning
(2) sintering atmosphere
The common sintering atmosphere in powder metallurgy is reduced atmosphere, vacuum, hydrogen atmosphere, etc.. The sintering atmosphere also has a direct influence on the properties of the sintered product.
Sintering in a reducing atmosphere prevent the burning loss and reduction of the oxide. Such as iron base and copper based products usually use furnace gas or dissociated ammonia, carbide, stainless steel often use pure hydrogen.
Active metal or refractory metal (such as beryllium, titanium, zirconium, tantalum), hard alloy containing TiC and stainless steel can be sintered in vacuum. Vacuum sintering can avoid the adverse effects of harmful components (H2O, O2, H2) in the atmosphere, and also reduce the sintering temperature (generally reduced by 100~150 degrees Celsius)