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Microstructural Characteristics, Crack Frequency and Diffusion Kinetics of Functionally Graded Ti-Al Composite Coatings: Effects of Laser Energy Density (LED)

  • E. O. Olakanmi
  • M. Sepako
  • J. Morake
  • S. E. Hoosain
  • S. L. Pityana
Solid Freeform Fabrication
  • 2 Downloads

Abstract

This study examines the dependence of microstructural characteristics, crack frequency and diffusion kinetics of functionally graded (FGM) titanium aluminide coatings reinforced with TiC on laser energy density (LED). Samples deposited on a Ti-6Al-4V substrate via single-step laser cladding (LC) were characterised with an optical microscope, scanning electron microscope/energy-dispersive x-ray spectroscopy and x-ray diffraction. LED set at 17.50 J/mm2 induced a thermo-positive reaction between FGM constituents, which resulted in the formation of intermetallic compounds (e.g., Ti2AlC, \( \gamma \) and \( \alpha_{2} \) matrix phases) with a microhardness greater than that of the substrate and least crack frequency. Variation in microhardness across the layers of sample fabricated with 17.50 J/mm2 is attributed to diffusion kinetics strongly influenced by laser-materials interactions due to the differing chemical composition across its volume. These outcomes provide guidance for a future study that engages the substrate’s pre-heat temperature in eliminating microstructural defects via a low-cost and time-effective single-step LC process.

Notes

Acknowledgements

This research was supported by the African Laser Center (ALC) under Grant No. CSIR-NLC (Reference LHIL 500 task ALC R008 & R010) and Botswana International University of Science and Technology (BIUST) Research Initiation Fund under Grant No. BIUST/ds/r&I/7/2016. Special thanks to the Office of the Deputy Vice-Chancellor Academic Affairs at BIUST for sponsoring the first author’s attendance at the 2018 Solid Freeform Fabrication Forum at University of Texas, Austin, USA, August 2018. The technical support from Mr. G. Rabalone and Mr. Madiba towards sample characterisation is acknowledged while Mr. Thatayaone Lekang’s assistance with Fig. 7b is appreciated.

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Copyright information

© The Minerals, Metals & Materials Society 2018

Authors and Affiliations

  • E. O. Olakanmi
    • 1
  • M. Sepako
    • 1
  • J. Morake
    • 1
  • S. E. Hoosain
    • 2
  • S. L. Pityana
    • 2
  1. 1.Botswana International University of Science and TechnologyPalapyeBotswana
  2. 2.Laser Enabled Manufacturing Research GroupNational Laser Centre/Council for Scientific and Industrial ResearchPretoriaSouth Africa

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