Surface treatment of titanium by Nd : YAG laser irradiation in the presence of nitrogen

This work presents the surface treatment of commercial titanium alloy by me ans of a Nd:YAG (1.064 mu m) laser in the presence of nitrogen. The treated surface was characterised by using scanning electron microscopy, atomic fo rce microscopy, X-ray diffraction, secondary ion mass spectrometry, UV-visi ble spectrophotometry and microindentation. Experimental results show the f ormation of a nitrogen-rich layer, 500 nm thick, with a surface morphology characterised by the presence of polygonal structures which suggest that me lting occurred under the action of the laser. The delta phase of titanium n itride was identified, in addition to a nitrogen in alpha-titanium solid so lution. The reflectance spectrum of the yellow-golden sample is similar to that of deposited titanium nitride thin films. The hardness of the treated surface was measured by microindentation and found to be 14 GPa, a value th ree times higher than that of the titanium alloy. In scratch tests the nitr ided layer detached at a load of 0.9 N.