Laser surface cleaning of carbonaceous deposits on diesel engine piston

► Carbonaceous deposits on piston surface were removed by nanosecond pulse laser cleaning. ► Thick and thin layers of stubborn contaminants were deposited non-uniformly on the surface. ► Main constituents of the deposits were Fe3C, Fe3O4, possibly FeOOH, oxygenated hydrocarbons and carboxylates. ► Fe3C was removed completely and oxygenated hydrocarbons as well as carboxylates were reduced significantly after laser cleaning. ► Oxidation and melting effect took place during laser processing.