An integrated experimental and computational approach to laser surface nitriding of Ti-6Al-4V

Titanium and its alloys have been commonly used in many biological and industrial applications owing to their excellent mechanical and physical properties. However, they have been specifically inadequate for biomedical implants due to their inferior tribological properties (low wear resistance, higher coefficient of friction, and lower hardness). As a remedy, the process of laser nitriding has emerged from the past few decades as a unique method for tailoring the surface microstructures and/or composition of titanium for enhanced tribological characteristics of titanium and its alloys. In the present study, a multiphysics computational model was developed to predict the nitrogen diffusion length into the Ti-6Al-4V alloy under various laser processing conditions (laser power and scanning speed). XRD, SEM and EDS analyses were also conducted for phase identification, microstructural investigation, and estimating the nitrogen concentration, respectively. Both computational and experimental results indicated that the depth of nitrogen diffusion increased with decrease in scanning speed, and subsequent increase in laser interaction time and increase in input laser energy density.

► Computational model was developed to simulate the laser nitriding process. ► Model precisely predicts the depth of nitrogen diffusion into the Ti-6Al-4V. ► XRD, SEM and EDS analyses evidenced the formation of nitrogen rich layer ((-Ti and (-TiN). ► Length of nitrogen diffusion increased with increase in laser energy density. ► Predicted nitrogen diffusional length was successfully validated (difference ±3-4%).