Feasibility studies of laser surface nitriding on Ti-6Al-4V alloy using a nitric acid solution

Feasibility studies for laser surface nitriding in a nitric acid solution were performed on a Ti-6Al-4V alloy. The susceptibility to surface cracking, hardness, bead shape, and the microstructure of the laser nitrided layers obtained at various concentrations of nitric acid were investigated over a wide range of processing variables. The results show that the hardness of the laser nitrided layer can be increased by increasing both the concentration of nitric acid and the energy density of the laser. The proposed process window shows that a high scanning speed, coupled with higher laser power, can result in crack-free nitriding, and also the hardness of the nitride layer can be finely controlled within this process window. Laser surface nitriding in nitric acid solution can increase the surface hardness without processinduced surface cracking. The proposed process is shown to be feasible and can be performed with a high degree of reliability.