Abstract: A process and device for the laser treatment of the internal surfaces of hollow bodies such as engine blocks with cylinder bores which consist of the matrix alloys such as a light-metal or aluminum, wherein a wear-resistant coating is applied to the working surfaces of the pistons within the cylinder. A probe enters the cylinder and includes the laser beam which produces a beam spot on the internal surface of the cylinder and applies an alloying powder at the focus of the spot using a continuously conveying protective gas. The probe is displaced along the axis of the cylinder and simultaneously rotated while the alloying powder is melted in the spot of the laser beam to a depth sufficient to form a wear-resistant coating which will not break loose during the normal operation and life of the engine block. The engine block can be fixed in a stationary position while the probe or probes move simultaneously within the cylinders to apply the hardened surface coating.