Coloring of titanium by pulsed laser processing in air

Surface treatments of titanium in air were performed by scanning with a Nd:YAG (lambda = 1.064 mum) pulsed laser beam at high repetition rate. Different colored samples were obtained depending on the laser accumulated fluence. The surface morphology and cross-sections of the coatings were studied by scanning electron microscopy, revealing the formation of a bi-layer structure consisting of a thin shallow layer covering a thicker layer. Compositional analyses performed by X-ray diffraction and Raman spectroscopy measurements revealed the presence of several oxide phases like Ti2O, TiO, Ti2O3 and TiO2 (rutile and anatase). Although changes in the colors of the samples may be correlated with the coating composition, the influence of light interference within the thin surface layer should not be discarded. (C) 2002 Elsevier Science B.V. All rights reserved.