Powder metallurgy bearing is made of metal powder and other antifriction material powder pressed, sintered, plastic and soaked. It has porous structure. After the infiltration of hot oil, the pores are filled with lubricating oil. In the process of working, the metal and oil are heated and expanded, and the oil is squeezed out of the pores. The friction surface is lubricated. After the bearing is cooled, the oil is sucked back into the pores.

Powder metallurgy bearings can not be lubricated for a long time.

The higher porosity of powder metallurgy bearings, the more oil storage, but the more pores, the lower the strength.

Such bearings are often in the mixed lubrication state, sometimes can form thin film lubrication. They are often used to supplement the difficult and light lo