Effects of surface roughness on mechanical properties of laser-cladding additively manufactured 316L stainless steel sheets

Laser-cladding (LC) additive manufacturing technology can be applied to repair local damage in steel structures. However, the process creates a distinctive surface morphology due to the overlap of weld beads on the repair surface, resulting in noticeable pit defects between adjacent weld beads. Under specific load conditions, these defects, or saying surface roughness, may cause significant stress concentration in localised areas of LC additively manufactured sheets. This stress concentration could adversely impact the mechanical properties of the LC additively manufactured sheets, including their stiffness, strength and ductility. This paper addresses this issue by testing smooth and rough surface tensile coupon specimens with different thicknesses produced by laser-cladding additive manufacturing technology. The rough surface specimens were geometrically characterised in detail by using 3D scanning technique, and the thickness distribution characteristics of the rough surface specimens were analysed based on the 3D scanning results. Tensile tests were then conducted on both smooth and rough surface specimens of different thicknesses, revealing that surface roughness indeed adversely affects the mechanical parameters of the LC sheets. The degree of degradation was also found to be related to the thickness of the specimens. Accordingly, a correlation analysis was performed among the degree of degradation, surface roughness and specimen thickness. Empirical formulae were proposed to predict the degree of degradation in the mechanical properties of the LC sheets due to surface roughness based on the results of the correlation analysis.