Effect of roller burnishing parameters on the surface integrity and high-cycle fatigue performance of AISI 4340 steel

Abstract This study investigates the effects of roller burnishing (RB) performed with different force and pass combinations on the surface integrity and high-cycle fatigue performance of quenched-and-tempered AISI 4340 steel. Fatigue specimens were roller burnished at 200 N (one pass) and 350 N (one and three passes). Surface roughness and subsurface microhardness measurements were performed. High-cycle, axial fatigue tests were conducted at various stress amplitudes and fatigue fracture surface examinations were carried out. RB improved surface roughness by up to 94 % compared with the unburnished condition. Turning and burnishing operations produced a shallow, softened layer whose depth varied with the applied parameters. The fatigue limit increased from 550 MPa to 900–925 MPa (64–68 % improvement), and at 800 MPa, fatigue life increased by approximately 89-fold; these gains rank among the highest improvements reported for burnishing-based surface treatments applied to AISI 4340 steel. Increasing the burnishing force enhanced fatigue resistance, whereas applying multiple passes at 350 N resulted in lower fatigue performance compared with a single pass at the same force, in line with the microhardness trends. Overall, the findings demonstrate that RB can significantly enhance the fatigue behaviour of AISI 4340 steel when process parameters are appropriately selected.