Structuring by laser remelting for removing waviness or generation of structures on metallic surfaces

• Applicant: Professor Dr.-Ing. Johannes Henrich Schleifenbaum
• Subject Area: Production Automation and Assembly Technology ; Coating and Surface Technology ; Synthesis and Properties of Functional Materials
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409767817

The Chair for Digital Additive Production DAP of RWTH Aachen University is investigating a new process for structuring metallic surfaces. The structuring is not based on ablation of material but on redistribution of material. The redistribution is achieved by laser remelting with modulated laser power. Characteristics and advantages of this innovative process are:- Manufacturing especially of periodic structures with small roughness, µm- to mm-wavelengths and heights of 2 to 500 µm- Structuring without ablation of material - Possibility for removing the waviness or structures from other manufacturing processes by structuring the inverse structure (“destructive interference”)- Structuring and laser polishing in one processing step- Homogenization of the chemical composition and generation of a fine grain structure in the surface layer and therefore enhancing the properties of the surface, e.g. regarding corrosion resistance or hardnessPossible applications are additive manufacturing (post processing of printed parts), mechanical engineering (post processing of milled precision parts), tool making (design surfaces, rewriteable metallic parts), aeronautics (fluid mechanics) and jewelry (design surfaces). However, due to the novelty of the process there are still many fundamental scientific questions to be answered:- Complete comprehension of the underlying mechanisms for structure formation. A paradox opposite behavior of steel alloy 1.2379 suggests that the process principle is not yet fully understood- “Inverse Problem”: Up to now mainly the modulation of the laser power was varied and the resulting structures were investigated. Which modulation is required to achieve a desired surface structure is only slightly investigated and only for periodic structures- Up to now the removing of structures and waviness by “Destructive Interference” is only investigated for 1-dimensional sinusoidal structures. The removing of 2-dimensional sinus and also aperiodic structures is not investigated yet- Transfer of the results on further metallic materials and investigation of the influence of the thermo-physical material properties on the structure formation- Modeling of structuring by remelting for investigating the influence of melt and solidification rate, volume change from solid to liquid and surface tension on the resulting structures- Extension of the process limits regarding small structures (wavelength < 100 µm) and area rate. At what point do physical principles limit the structuring process? Can a melt pool be too small or laser modulation too fast for structure formation?- Investigation of structuring by laser remelting for 3D surfaces (angle of incidence, borders between subareas) on simple 3D geometriesThese scientific questions shall be investigated in the applied project in a close collaboration between the chair DAP of RWTH Aachen University and the National Institute of Aviation Technologies NIAT in Moscow.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research
• Cooperation Partner: Dr.-Ing. Oleg Oreshkin