Effects of shielding gas on laser surface processing

Abstract

Laser surface processing is widely used in modern manufacturing to enhance surface properties such as roughness and oxidation resistance. In this thesis, laser surface processes are defined to be low-power processes such as laser polishing, laser cleaning and laser engraving. A key factor that influences the outcome of these processes is the selection and control of shielding gas. Shielding gas controls oxidation, stabilizes the melt pool, and directly influences the final surface quality and the mechanical properties of the processed material. This thesis presents a comprehensive literature review on the effects of various shielding gases including argon, nitrogen, oxygen, carbon dioxide, and compressed air on laser-based surface treatments. The findings show that inert gases like argon and nitrogen offer the best performance in oxidation prevention and surface quality, making them suitable for precision applications. Reactive gases such as oxygen and carbon dioxide increase material removal rates, but they introduce surface roughness and oxidation-related defects. Compressed air is a cost-effective alternative for applications where surface roughness and oxidation are not critical. In addition to gas type, the study highlights the importance of gas flow parameters and delivery methods. Variables such as flow rate, pressure, nozzle distance, and shielding approach (chamber vs. nozzle) have a substantial effect on surface quality because they determine the stability, coverage, and effectiveness of the shielding gas, directly influencing melt pool behavior, oxidation prevention, and the formation of surface defects. Proper optimization of both gas selection and the method of introducing gas to the object is essential for achieving high-quality results in laser surface processing.