METHOD OF IMPROVING WEAR-RESISTANCE CHARACTERISTICS OF A POROUS METAL MACHINE PART

摘要

A method of improving wear-resistance characteristics of a porous metal machine part by densifying the part throughout its thickness. The method includes the steps of ultrasonically cleaning the part to remove impurities from the pores of the part and then drying the part. The part is then exposed to cryogenic temperatures generated by a cryogenic liquid during a period of time. The period of time is divided into three cycles--a gradual cooling cycle wherein the part is gradually cooled from ambient temperature to a temperature of between minus 173 and 212 DEG C; a soak cycle wherein the part is maintained at a temperature of between minus 173 and 212 DEG C; and a gradual warming cycle wherein the part is gradually warmed to ambient temperature. The surface of the metal part is thereafter removed to a depth of from .000254 to .0254 cm to expose a new densified metal wearing surface; and the newly-exposed metal surface is polished.