부산대학교 도서관

One of the exciting applications of laser directed energy deposition (LDED) is the fabrication of complex-shaped engineering components involving graded composition. In the present work, a 2 kW fibre laser-based LDED system is used to deposit copper-nickel (CuxNi(100−x) (x = 25, 50, and 75)) layers on copper (Cu) substrate. The single tracks are deposited at different combination of laser power, scan speed, and Cu-Ni compositions. Track geometry (width and height) indicates direct and inverse dependence with laser power and scan speed, respectively. For same LDED processing parameters, there is lower track height and wider track width with increasing Cu in Cu-Ni composition due to improved wettability. Further, analysis of variance (ANOVA) shows that laser power and scan speed are more significant for track width and track height, respectively. Graded bulk structures built at identified process parameters are characterized using optical microscopy, microhardness, and single cycle automated ball indentation (SC-ABI). Deposited Cu-Ni graded bulk has a density of > 99% with pure Cu and Ni phase. The microscopy analyses reveal defect-free deposition with fine dendritic growth in the bottom and middle layers, while equiaxed grains are observed in top layers. Microhardness measurements show a smooth hardness transition from deposit to the substrate with higher hardness. SC-ABI presents an increase in energy storage capacity by 2.25 times with the increase in Cu percentage. This work paves a way for fabricating Cu-Ni graded components for manufacturing engineering components. [ABSTRACT FROM AUTHOR]