A comparative study of 3D laser surface modification and the humping phenomenon

Surfi-Sculpt^® is a three dimensional surface modification technique that enables functional features to be formed from a substrate material by repeated swipes of a highly focused power beam. Successive swipes of the beam can move molten material so that a protrusion builds up on the surface of the substrate. Characteristics thought similar to the weld instability phenomenon known as humping, have been observed in the Surfi-Sculpt process and it has been proposed that the processes may be related. However, in the Surfi-Sculpt process, the heat input is distributed over a longer duration and at critical time intervals when compared to conventional high speed welding. This work identifies how the Surfi-Sculpt technique can be compared with previously published work on humping parameters and theories. Surfi-Sculpt experiments were carried out with beam swipe speeds between 200 and 1000 mms⁻¹ (within the range of published weld humping speeds of 20 to 1500 mms⁻¹). A single mode fibre laser operating between 200 and 260W was used in this work and the beam was manipulated by an optical scanning system. High speed imaging with dual 500W laser illumination was used to compare experimental results of the two processes with the objective of gaining a greater understanding of the parameter to feature shape relationships and the theory involved in the material movement.