Microstructural evaluation of maraging 300 steel surface treated by Nd:YAGlaser

Maraging steels are Ni-Co-Mo-Ti alloys of ultra-high resistance and spread application, since defense and nuclear industry until aeronautic components, pressure vessels and sports industry. Maraging steels are composed by a metastable martensitic microstructure. This work aims to evaluate the microstructural behavior of a maraging 300 steel after superficial laser treatment to reduce the oxygen permeability in the structure, increasing the mechanical resistance at elevated temperatures. Microstructural characterization was evaluated by scanning electron microscopy (SEM), X-ray diffraction and roughness by profilometry.The laser path typically of 500 μm wide was observed. Surface roughness results were R_a= 634 ± 160 nm; R_q= 789 ± 185 nm and R_t= 8,2 ± 3,2 nm. Laser treated sample exhibited, in addition of diffraction peaks due to the martensitic phase, additional peaks related to austenite phase and Fe₂N/Fe₃N.Therefore, laser surface nitriding can be used to change the surface properties. (author)