Investigating the effects of processing head and substrate inclination on the EHLA process: Impact on track formation and surface roughness

Extreme high-speed laser material deposition (EHLA) is a laser-based coating process known for its high deposition rates and excellent resource efficiency. To further increase productivity, higher laser powers and powder feed rates are increasingly used, but this also raises the thermal load on the processing head due to back-reflected radiation. Inclining the processing head or substrate helps deflect this radiation, while also enabling coatings in geometrically constrained areas, such as internal surfaces. However, inclination introduces asymmetries in the powder and laser distribution, potentially affecting track formation and melt pool behavior. This study investigates how inclination between the processing head and a rotationally symmetric substrate influences track geometry, surface quality, dilution, and thermal impact. Two inclination configurations were examined across a range of angles, with systematic variation of feed and rotation direction to simulate pushing and pulling deposition strategies. The results reveal that inclination has a significant and configuration-dependent effect on surface roughness, build-up volume, powder catchment efficiency, and thermal penetration. Variations in asymmetry orientation relative to the motion direction lead to measurable differences in coating properties. The findings offer new insights into optimizing EHLA process parameters for inclined setups, contributing to more robust and application-specific coating strategies.