Microstructural aspects of laser surface treatment of commercially pure titanium

Commercially pure (CP) titanium was subjected to cw-CO2 laser surface treatment. The treatment was carried out using a side-by-side dual laser beam. The initial and surface treated materials were subjected to structural and microstructural examination. It was found that the microstructure in the laser treated zone changed from an alpha-phase present in the non-remelted material to martensite alpha' t as a consequence of the very high rates of cooling. An increase in the diffraction reflections originating from the (101) titanium plane was observed in the remelted sample. Despite the fact the laser treatment was conducted in a protective gas shield, limited oxidation occurring due to the high reactivity of titanium was observed. Analysis of the remelting parameters in connection with the macroscopic evaluation and microstructural changes in the surface layer allowed the relationships facilitating the shaping of the melting zone geometry, as well as the scope of microstructural changes to be determined.