Title: Effect of laser scanning speed on surface properties of Ti-Si laser clad intermetallic coatings fabricated on Ti-6Al-4V alloy

Authors: M.F. Phala; A.P.I. Popoola; M. Tlotleng; S.L. Pityana

Addresses: Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, P.M.B X680, Pretoria 0001, South Africa ' Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, P.M.B X680, Pretoria 0001, South Africa ' Council of Scientific and Industrial Research, National Laser Centre, Building 46F, P.O. Box 395, Pretoria 0001, South Africa ' Council of Scientific and Industrial Research, National Laser Centre, Building 46F, P.O. Box 395, Pretoria 0001, South Africa

Abstract: A binary Ti-Si (1 : 1) alloy coating was fabricated on Ti-6Al-4V alloy using laser cladding technique where Neodymium yttrium aluminium garnet laser was utilised. Micro-atomised powders of Ti and Si were used for deposition of multi-track clad coatings utilising power of 1.5 kW and a varied speed of 1.2 m/min, 1.6 m/min and 2.0 m/min. Scanning electron microscope coupled with energy dispersive spectrometer was used for microstructural characterisation and elemental analysis while a digital light microscope was used for optical imaging and coating thickness measurements. Phase identification was conducted using X-ray diffraction analyser and transverse microhardness evaluated at 100 gf for 10 s dwell time was achieved with the use of a Vickers hardness machine. The laser fabricated coatings were found to exhibit a decrease in grain size with an increase in the laser scanning speed. The microstructure of the coatings ranged from irregular refined grains, faceted grains and lamellar eutectic network of Ti_SS + Ti₅Si₃. The hardness of the coatings exhibited Ti, Si, TiS₂ and Ti₅Si₃ phases averaged a 247.4% increase with maximum hardness recorded at 1.2 m/min scanning speed.

Keywords: laser cladding; titanium; Ti₅Si₃ phase; scanning speed; coating thickness; microhardness; microstructure; HAZ; heat affected zone; substrate; grain structure.

DOI: 10.1504/IJMMP.2018.097217

International Journal of Microstructure and Materials Properties, 2018 Vol.13 No.5, pp.331 - 343

Received: 17 Jan 2018
Accepted: 09 Jul 2018
Published online: 04 Jan 2019 *

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