The controlled porosity of powder metal parts permits their impregnation with oil or a resin. Also, with suitable compaction techniques, porosity can vary in different areas of the powder metal part. Oil-impregnated powder metal bearings have been used in automobies since the late 1920s.
Impregnation is achieved by soaking the parts in heated oil or by vacuum techniques.
When friction heats the part, the oil expands and flows to the bearing surface. On cooling, the oil returns into the metal's pores by capillary action. All All . . Bearings Structural . Infiltration . . .