Abstract: The present invention relates to a hydraulic piston and a process for its surface treatment in order to improve above all the wear resistance and corrosion resistance at the surface of the piston. As a favorable manufacturing process for the surface treatment of an above-mentioned hydraulic piston, a multistage process is disclosed which arranges a nitrocarburization with a subsequent oxidation and a following mechanical solidification of the oxidized surface for the piston. As a result, several superposed layers—layer of oxide, connecting layer, diffusion layer—develop at the piston surface which exhibit the desired qualities.

Abstract: The present invention relates to a piston for a hydraulic pressure chamber, especially a piston bore of a spot-type disc brake, wherein the piston is configured as a bowl-shaped hollow cylinder that is open on one side and made from a metal blank of a constant wall thickness in a forming operation. The piston has a bottom to which hydraulic pressure is applicable and a piston wall which, at its open end, passes over into a rim that has a circular abutment surface. Especially in view of conventional cast pistons, an object of the present invention is related to providing a piston which permits being manufactured by means of a simple forming operation, which can be configured as light as possible and with low expenditure in material, without limiting the stress capacity of the piston.