SURFACE ANALYTICAL STUDIES OF A LASER NITRIDED TI-6AL-4V ALLOY - A COMPARISON OF SPINNING AND STATIONARY LASER-BEAM MODES

X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterise titanium nitride phases in a Ti-6Al-4V alloy at different depths, produced by laser nitriding with spinning and st ationary beams. The XPS results showed, via deconvolution methods, tha t the line shapes and peak positions of Ti2p are dependent upon the ni trogen concentration at different depths and were able to provide more precise information on the TiNx substoichiometry. XRD and XPS have le d to the conclusion that with a spinning beam, the large dendritic str ucture which formed in Zone 1, about 50 mu m depth, consisted of TiN0. 80 on the top surface and TiN0.85 at a depth of 35 mu m; a needle-like structure which formed in Zone 2, about 350 mu m below the surface, c onsisted of TiN0.3 and martensitic alpha'-Ti. With a stationary beam, the large dendritic structure was TiN0.75 on the top surface and TiN0. 50 (cubic) in the melt pool below 50 mu m depth; also in the melt pool were TiN0.3 and martensitic alpha'-Ti phases. (C) 1998 Acta Metallurg ica Inc.