Microstructure, hardness and corrosion properties oflaser processed Ti6Al4V-based composites
(1. Department of Chemical, Metallurgical and Materials Engineering,
Tshwane University of Technology, Pretoria 0001, South Africa;
2. Council for Scientific and Industrial Research, National Laser Center, Pretoria 0001, South Africa)
Tshwane University of Technology, Pretoria 0001, South Africa;
2. Council for Scientific and Industrial Research, National Laser Center, Pretoria 0001, South Africa)
Abstract: Nb and Ti-13Nb powders were used for improving the surface of Ti6Al4V alloy. The deposition of the powders was carried out at various laser powers. The scanning electron microscopy (SEM)-EDS and optical microscopy were used for characterization. X-ray diffractometer (XRD) was used for analyzing the elemental composition and phase constituents. The hardness, wear and corrosion properties were achieved. The corrosion and the wear behaviours of the deposited layers were studied in a Hanks solution (simulated body fluid, SBF). The microstructures of Nb coatings reveal the presence of orthorhombic, dendritic α″ and metastable β-Nb phases which produce uneven hardness with an average of HV 364. For Ti-13Nb coatings, martensitic α′ and metastable β-Nb phases with an average hardness of HV 423 were observed. The resistance of wear on dry sliding of Ti-13Nb coating is attributed to the increase in hardness. Experimental results indicate that deposition of Nb and Ti-13Nb on Ti6Al4V grossly reduces the mass fractions of Al and V in all coatings. In SBF, Nb reinforcement produces the best coating that reveals the best wear and corrosion resistances as compared with the substrate. Hence, this coating will perform best for orthopaedic implant material enhancement.
Key words: Ti6Al4V-based composite; Nb; simulated body fluid; laser deposition; passivation; microstructure; corrosion property