SURFACE DENSIFICATION OF MACHINE COMPONENTS MADE BY POWDER METALLURGY

摘要

A sintered powder metal part is surface densified by surface heating followed by repressing. Surface heating is preferably done to a temperature which is just below the critical temperature where the steel alloy material of the part transforms from a ferritic to an austenitic microstructure. Repressing is in a die set which is smaller than the part by 10 % of the surface heated depth. The hot skin is compressed and densified between the die and the cooler, and therefore less malleable core of the part. Following surface densification, the part may be resintered and/or heat treated.