CO2 laser nitriding of titanium

Samples of pure titanium were laser nitrided by continuous wave CO2 laser irradiation in mixtures of nitrogen and argon gas with different ratios. In all cases, TiN formed in the surface. The properties and the characteristics of the processed samples were evaluated using nanoindentation technique, optical microscopy, surface roughness measurements, X-ray diffraction and wear resistance measurements. It was found that the nitrogen content in the gas atmosphere has a massive effect on the microstructure and the mechanical properties of the laser nitrided samples. For all treated samples, the mechanical properties are improving with the nitrogen content in the gas atmosphere. Moreover, the thickest TiN layers with high values of the microhardness and good wear resistance were obtained for the titanium sample that was treated in 80% N2 and 20% Ar. In addition, the strain and the grain size of the coatings formed at the surface of the laser nitrided titanium samples were determined from X-ray data.