Laser cladding using thin wires (<0.8 mm) presents significant potential for applications requiring high precision and minimal heat input, such as coatings for nuclear fuel rods. This work investigates Laser Micro-Wire Cladding (LMWC) using a 200 µm wire, showing the transition from fundamental process studies on single tracks and flat substrates to the application of FeCrAl coatings on 15-15Ti and 316L tubes relevant to nuclear fuel rods. High-resolution high-speed imaging (HSI) experiments revealed unique melt transfer characteristics, including a stable melt bridge and drop deposition mode. The mechanisms governing these modes were analysed. A novel wire-bending technique was developed to enhance process stability, crucial for consistent deposition. This understanding facilitated the successful deposition of thin (135 µm), low-dilution (< 7%), defect-free clad layers onto thin (500 µm) substrates. Characterization indicates that the coatings meet demanding requirements for nuclear applications.

This study experimentally investigated laser micro-wire cladding (LMWC), an additive manufacturing process that covers a substrate with cladding tracks having small cross-section area and low dilution. Laterally fed 200 μm thin steel wire and a continuous laser beam were used to deposit single tracks with widths and heights between 220 to 370 μm and 115 to 180 μm, respectively. By carefully selecting setup and process parameters, tracks with 0 to 35 % dilution and deposition speeds up to 20 mm/s were realised. An advanced high-resolution high-speed imaging technique was used to study the melt transfer and evaluate process stability. Specifics of LMWC compared to regular sized laser wire cladding are proposed along with explanations based on size effects. Cross-section analysis of the single tracks gave quantitative data that was used together with process parameters to relate between track geometry, dilution, deposition speed, and laser power. A novel wire-bending technique was developed that improved process stability and overall track quality. Finally, two 120 μm thin demonstration clads were manufactured, using two different wire materials by overlapping tracks. The results show the potential of LMWC for thin coatings especially on thin substrates, micro scale repair of components, or further development towards layer-by-layer laser metal wire deposition (LMWD) with high geometric resolution.