Composite bearing material with polymer filled metal matrix interlayer of distinct metal particle sizes and method of making same

A composite bearing material suitable for both dry and lubricated bearing applications comprising:

• (a) a metal backing;
• (b) a porous metal interlayer on said metal backing, said porous metal interlayer consisting essentially of a relatively non-homogeneous mixture of particles form two distinct particle size ranges including a relatively fine powder range of about -300 mesh and less and a relatively coarse powder range form about -60 to +150 mesh, said relatively fine powder range comprising from about 5% to about 30% by weight of the total powder constituting said porous metal interlayer and wherein a substantial portion of said relatively fine powder is segregated from the particles in said coarse powder range to the innermost surface of said porous metal interlayer adjacent said metal backing and bonded to said metal backing and certain of said particles within said relatively coarse range, said particles from said relatively coarse range being bonded to one another and forming a open structure of numerous pores throughout at least the outermost surface of said porous metal interlayer;
• and
• (c) a polytetrafluoroethylene based composition substantially filling the pores of said porous metal interlayer and forming a surface layer on the bearing material, said polytetrafluoroethylene based composition comprising from about 2% to about 10% by volume of at least one material selected from the group consisting of tin bronze and other copper alloys, as well as mixtures thereof;
• from about 5% to about 30% by volume of at least one material selected from the group consisting of metallic lead, metallic cadmium, an oxide of lead, and an oxide of cadmium, as well as mixtures thereof;
• from about 5% to about 30% by volume of at least one material selected from the group consisting of natural graphite and artifical graphite, as well as mixtures thereof;
• and the remainder comprising polytetrafluoroethylene.