Improving the surface integrity of laser cladded layer by ultrasonic-assisted burnishing at medium temperature with considering initial surface conditions

Abstract

Improving the surface integrity of laser cladded layer via burnishing is an important research topic in remanufacturing field. However, the initial surface roughness condition induced by mechanical machining generates great influence on the strengthening mechanism of subsequent burnishing. In this study, the effects of ultrasonic-assisted burnishing (UB) and ultrasonic-assisted warm burnishing (UWB) on the surface integrity of laser cladded layer were analyzed when treated on different surface conditions obtained by turning with different feed parameters. The results indicated that both the UB and UWB treatments would cause great improvements in microhardness, surface roughness including height and functional parameters, and residual stress of the laser cladded layer when compared to those by turning. First, the severe plastic deformation in UB and UWB treatments counteracted the thermal softening effect in turning process, so that the machined surface could maintain high hardness. Second, UB treatment reduced the roughness by 70% compared with turning, while the surface roughness after UWB treatment was even 30% lower than that obtained by UB. Third, the tensile residual stress shifted to deep compressive state by both UB and UWB treatments, though the thermal load in UWB generated a negative effect on generating compressive residual stress. According to the surface integrity evaluation results by radar diagrams, turning with feed f = 0.2 mm/r and UWB is preferred in machining of the laser cladded layer for enhanced surface integrity. On the basis of this research, it is expected to achieve the purpose of high-efficiency and high-quality cutting of the laser cladded layer.