Impact of process parameters and cutting direction on surface integrity and microstructure in fiber laser micro-cutting of Nitinol stents

This study presents an experimental analysis of the fiber laser cutting process of Nitinol stents to characterize the influence of spot overlap and pulse energy on surface roughness, entry kerf width, dross formation, and oxidation. The surface topographies and the impact of the cutting direction on entry kerf width, dross, and oxidation were discussed from the experimental results. Microhardness and microstructure were analyzed to find any internal heat effect on the cut sample. Results indicate that spot overlap has a significant repercussion on surface roughness and dross formation, minimizing both indicators at the highest evaluated level (83.31%). The highest pulse energy level (32.16 mJ) resulted in minimized surface roughness (~ 1 µm), whereas the lowest dross and oxidation values were obtained with the lowest pulse energy level (30.82 mJ). Two different topographies were obtained: striated and amorphous topographies. The striated topography was associated with higher roughness but lower dross and oxidation, in contrast to the amorphous topography. The laser cutting direction exhibited a strong relationship with dross formation, oxidation, and entry kerf width.