Study of micro/nanostructures formed by a nanosecond laser in gaseous environments for stainless steel surface coloring

Micro/nanostructures are fabricated on the stainless steel surfaces by a nanosecond laser in different gaseous environments, including air, O2, N2 and Ar. Our results indicate that the dimensional feature of the micro/nanostructures is greatly affected by laser scanning speed as well as gaseous environment. The chemical composition of the structures can be flexibly adjusted by laser processing parameters. Oxygen-rich environment is found to boost the growth of the nanostructures. The coloring by the laser processing can be achieved on the laser treated stainless steel surfaces. The multicolor effect on the surfaces is found to be attributed to both feature dimension and chemical composition of the structures. The coloring of the metal surfaces has promising applications in surface marking and code identifying.