Surface structuring by laser remelting of metals

Abstract

Surface structuring by remelting with laser radiation is a new approach to shape metallic surfaces ("WaveShape"). In this structuring process, surface material is reallocated in its molten state instead of being removed, because the process is based on the new active principle of remelting. The surface structure and the microroughness result from a laser-controlled melt pool due to surface tension. Basic research has been conducted with promising results, especially for the hot work steel 1.2343. Since remelting is a thermally driven process, significant differences between metallic materials were expected due to their thermophysical properties such as thermal conductivity, absorption coefficient, viscosity, heat capacity, etc. Therefore, the presented research soughed to expand the spectrum of processable materials. Within the framework of our investigation, we compared the achieved structure height as well as melt pool dimensions for six different materials. Furthermo re, we successfully tested new structuring strategies such as not linearly shaped scanning vectors to create innovative surface structures on all materials investigated. The biggest structures were achieved on the titanium alloy Ti6Al4V and the nickel based super alloy IN718. Finally, an approach of reverse structuring was investigated in order to erase existing structures and achieve a smoothed rewriteable metallic surface. The results show that surface structuring by laser remelting is well suited to process a wide range of different metals and to achieve a broad variety of different structures as well as to effectively erase existing surface structures such as milling marks

Additive and Substractive Surface Structuring by Femtosecond Laser Induced Material Ejection and Redistribution

“…Under certain circumstances (a more dedicated discussion is in the following paragraphs), the ejected species land on the adjacent site, adhere to the vicinity of ablation site, and form an accumulation. Such a material redistribution is somehow similar to the work of Temmler, et al [15] (although the mechanism governing the material displacement is totally different). By raster scanning a small area on a substrate, the accumulation continues on and eventually forms a three-dimensional structure by itself, which will be termed as additive structures (AS), as indicated by the white bump in Figure 1a.…”

“…In this case, the consequent pulse-by-pulse ablation with a scan from left to right leads to a pronounced microstructure on the left side of the laser-processed area, as displayed in Figure 2a. Other possible mechanisms of material re-deposition include Marangoni melt flow and recoil vapor pressure [15,20]. However, these effects fail to explain why the accumulated material is observed above the ablated area, but not outside it.…”

Surface Structuring by Laser Remelting (WaveShape): Microstructuring of Ti6Al4V for a Small Laser Beam Diameter and High Scan Speeds

“…Surface structuring by laser remelting (WaveShape) is a novel surface structuring process used for structuring metallic surfaces in the micro-and millimeter range by power modulation of a laser beam source. In contrast to other laser structuring processes, surface features are not generated by localized ablation but created by redistribution of molten material at the surface [20,21]. An attempt for modeling of the WaveShape process of Ti6Al4V was presented by Sharma et al [22].…”

A Preliminary Study to Enhance the Tribological Performance of CoCrMo Alloy by Fibre Laser Remelting for Articular Joint Implant Applications

“…The direction (upward/downward) of the ripple features indicated the moving path of the laser beam in the laser remelting experiment. Temmler et al [29,30] proposed a schematic model to explain that the resulting surface topography (i.e., surface ripples) in laser remelting is controlled by the variation of the melt pool volume and the movement of the three-phase line, namely the boundary between liquid and solid material and atmosphere, in the area of the solidification front. The ripple formation results from the fluctuation of the melt pool volume, which can be precisely modulated by the modulation of laser power.…”

“…Laser remelting is an effective approach to modify the surface structure and properties of metallic materials, such as roughness, hardness and corrosion resistance [29,30]. It is commonly employed as a post-process treatment for enhancing the homogeneity in microstructure and reducing the porosity in the surface layer [31][32][33][34].…”