Microstructures, compressive residual stress, friction behavior, and wear mechanism of quenched and tempered shot peened medium carbon steel

This research studied the effect of quenching and tempering combined with shot peening on the wear and friction behavior of medium carbon steel used in fasteners under lubricated sliding conditions. Shot peening and quench-tempering processes both produced higher compressive residual stress on the disks. During tribo-tests, the tangential shear force and frictional heating generated by frictional contact produced significant plastic deformation by a ratchetting process. The pearlite/tempered martensite beneath the worn surface experienced significant plastic deformation along the sliding direction. Shot peening resulted in more wear and overfoldings on the surface of soft quenched-tempered and shot peened disks rather than on the hard quenched-tempered and shot peened disks. The tempered martensitic/pearlite microstructures on the top of worn surfaces displayed mechanical fracture, fragmentation, and cracks. •Shot peening and quench-tempering processes both produced higher compressive residual stress on the disks.•On the harder tempering disk, compressive residual stress can restrain crack initiation and propagation more effectively.•The pearlite/tempered martensite beneath the worn surface of the disks had significant plastic deformation.•Oxide particles were generated on the disk surface and acted as third bodies producing abrasive wear and ploughing wear.•The oxide particles adhered to the ball and resulted in smearing on the disk surfaces due to the balls' higher hardness.