Electrochemical properties of the laser nitrided surfaces of Ti–6Al–4V alloy

Laser gas-assisted nitriding of Ti–6Al–4V alloy has been considered and the electrochemical response of the nitrided surfaces was examined. A CO2 laser delivering output power in 1500 Hz pulses was used to irradiate the alloy surface. XRD, EDS and SEM were used for microstructural analysis and surface morphology of the nitrided surfaces prior and after the electrochemical tests. To monitor the surface phenomena occurring during the nitriding process, a CCD camera was used. Potentiodynamic and petontiostatic polarization tests were carried out. It is found that δ-TiN and ε-Ti2N were the dominant phases in the surface region of the nitrided workpieces. The depth of nitride layer extends beyond 50 μm below the surface. No microcracks or voids were observed in the nitrided layer and the layer thickness extended homogeneously over the workpiece surface. Some scattered pit sites were observed at the nitrided surfaces, which may be attributed to the irregularly scattered surface texture peaks.