Abstract: In the piston and piston-rod guide unit for hydraulic shock absorbers the piston-rod guide (2) includes an annular piece (3) provided with a central orifice (5) for the piston rod and an elastic sealing ring (4), and the piston (1) is a body of revolution with a convex generatrix. The external surface of the piston is coated with an anti-friction piston coating (9) advantageously including polytetrafluoroethylene and having a uniform piston coating thickness. The central orifice (5) of the annular piece has an internal wall coated at least partially with a guide coating (6) having a uniform guide coating thickness equal to that of the piston coating (9) and a coating composition which is the same as that of the piston coating. These coatings (6,9) are between 20 to 60 micrometers thick and are charged with ceramic particles and a pigment in the polytetrafluoroethylene, in order to reduce friction and improve wear resistance.

Abstract: A friction material for a lubricated tribological system, particularly for a synchro of a gear box, consists of a bronze or steel matrix containing from 5 to 40% by weight of embedded hard particles. A 90% portion of the embedded hard particles have a particle size of from 50 and 300 micrometers. These hard particles consist of an alloy including Cr, Mo, W, V, Ni, Zr, Al and/or Ti and carbides of Cr, Mo, W and V; nitrides of Al and Mo; and/or oxides of Cr, Ni, Zr and Ti. The hardness of the hard particles is advantageously above 600 HV 0.1. This friction material has a comparatively high friction coefficient which is constant independent of variations of sliding speed.

Abstract: A material for friction components made by a process including the steps of providing a first powder consisting of grains of a comparatively harder material with a comparatively higher coefficient of friction and an average grain size of from 60 to 100 microns, and a second powder consisting of grains of comparatively softer material with a comparatively lower coefficient of friction and an average grain size of from 60 to 100 microns; mixing the first powder and the second powder to form a powder mixture having a total volume; and subjecting the powder mixture to a pressure and temperature sufficient for the grains of the first powder to be intermixed with the comparatively softer material of the second powder so that the comparatively harder material substantially fills an intergranular space between the grains of the first powder to form the material for the friction components, the comparatively harder material occupying from 1/3 to 4/5 of the total volume of the powder mixture.