A STUDY INTO EFFECTS OF CO2-LASER MELTING OF NITRIDED TI-6AL-4V ALLOY

Multiple treatment of engineering surfaces can provide improved surfac e properties that cannot be obtained by a single surface treatment, Co nsequently, this study investigates tile effects of laser melting on t he microstructures of plasma nitrided Ti-6Al-4V alloy, The study consi sts of two parts, In the first part, governing equations pertinent to the laser melting process are developed, and temperature variation acr oss the melted zone is predicted, In the second, an experiment is cond ucted to nitride the surface of the alloy through plasma nitriding pro cess and to melt the plasma nitrided and the untreated alloy surfaces with a CO2 laser beam, The resulting metallurgical changes are examine d using x-ray diffraction (XRD), energy-dispersive spectrometry (EDS), and scanning electron microscopy (SEM) techniques. It is shown that t hree distinct nitride layers are formed in the vicinity of the alloy s urface prior to the laser melting process, and that after the melting profess nitrided species are depicted while cellular and dendritic str uctures are formed, In addition, the structure consisting of transform ed beta containing coarse and fine acicular alpha is observed in the m elted regions.