A single parameter approach to enhance the microstructural and mechanical properties of beta Ti-Nb alloy via open-air fiber laser nitriding

Chi Wai Chan, Xianwen Chang, Mohammad Amin Bozorgzadeh, Graham C. Smith, Seunghwan Lee*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

In this study, the idea of applying open-air laser nitriding to improve the microstructural and mechanical properties of beta Ti-45 at.% Nb alloy was demonstrated. Surface cracking after laser nitriding is one of the main reasons impeding direct translation of the laser nitriding technique from the laboratories to industries as cracks can be the weak points to initiate mechanical and corrosion failures in long-term usage. With proper selection of duty cycle (DC) between 40% (modulated mode) and 100% (continuous wave, CW mode) to control the laser energy input and laser-material-gas interaction time, the cracking problems of laser nitriding can be alleviated and even solved. A crack-free and uniformly gold-coloured nitrided surface was successfully obtained at the DC of 40% in this study. The morphology, microstructure, composition and mechanical properties of the nitrided samples were studied and analysed by optical microscopy (OM), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Vickers micro-hardness tests. The OM results indicated that minimum overlapping between the laser tracks would give desirable results to obtain the crack-free surface. The measurements from the SEM micrographs indicated the depth of the laser-nitrided areas ranged between 22 and 43 μm. The XRD findings showed that a clear conversion of the TiNb surface to a nitride as a result of laser nitriding was observed. The maximum hardness, as measured by the Vickers method in cross-sections, lie in the range of 780 to 870 HV after laser nitriding. To summarise, control of DC to obtain a crack free and quality surface via fiber laser nitriding in open air is a simpler and quicker approach in comparison with the conventional substrate preheating and nitrogen (N) dilution approaches. The single-parameter approach is more efficient than parameter optimisation via design of experiments (DOE) employed in conventional methods.
Original languageEnglish
Article number125269
JournalSurface and Coatings Technology
Volume383
Number of pages11
ISSN0257-8972
DOIs
Publication statusPublished - 2020

Keywords

  • Beta Ti-Nb alloys
  • Laser nitriding
  • Fiber laser
  • Titanium nitride (TiN)
  • Orthopaedics

Cite this

@article{7c1a71fa889844b0a567cb8204069be0,
title = "A single parameter approach to enhance the microstructural and mechanical properties of beta Ti-Nb alloy via open-air fiber laser nitriding",
abstract = "In this study, the idea of applying open-air laser nitriding to improve the microstructural and mechanical properties of beta Ti-45 at.{\%} Nb alloy was demonstrated. Surface cracking after laser nitriding is one of the main reasons impeding direct translation of the laser nitriding technique from the laboratories to industries as cracks can be the weak points to initiate mechanical and corrosion failures in long-term usage. With proper selection of duty cycle (DC) between 40{\%} (modulated mode) and 100{\%} (continuous wave, CW mode) to control the laser energy input and laser-material-gas interaction time, the cracking problems of laser nitriding can be alleviated and even solved. A crack-free and uniformly gold-coloured nitrided surface was successfully obtained at the DC of 40{\%} in this study. The morphology, microstructure, composition and mechanical properties of the nitrided samples were studied and analysed by optical microscopy (OM), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Vickers micro-hardness tests. The OM results indicated that minimum overlapping between the laser tracks would give desirable results to obtain the crack-free surface. The measurements from the SEM micrographs indicated the depth of the laser-nitrided areas ranged between 22 and 43 μm. The XRD findings showed that a clear conversion of the TiNb surface to a nitride as a result of laser nitriding was observed. The maximum hardness, as measured by the Vickers method in cross-sections, lie in the range of 780 to 870 HV after laser nitriding. To summarise, control of DC to obtain a crack free and quality surface via fiber laser nitriding in open air is a simpler and quicker approach in comparison with the conventional substrate preheating and nitrogen (N) dilution approaches. The single-parameter approach is more efficient than parameter optimisation via design of experiments (DOE) employed in conventional methods.",
keywords = "Beta Ti-Nb alloys, Laser nitriding, Fiber laser, Titanium nitride (TiN), Orthopaedics",
author = "Chan, {Chi Wai} and Xianwen Chang and Bozorgzadeh, {Mohammad Amin} and Smith, {Graham C.} and Seunghwan Lee",
year = "2020",
doi = "10.1016/j.surfcoat.2019.125269",
language = "English",
volume = "383",
journal = "Surface and Coatings Technology",
issn = "0257-8972",
publisher = "Elsevier",

}

A single parameter approach to enhance the microstructural and mechanical properties of beta Ti-Nb alloy via open-air fiber laser nitriding. / Chan, Chi Wai; Chang, Xianwen; Bozorgzadeh, Mohammad Amin; Smith, Graham C.; Lee, Seunghwan.

In: Surface and Coatings Technology, Vol. 383, 125269, 2020.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - A single parameter approach to enhance the microstructural and mechanical properties of beta Ti-Nb alloy via open-air fiber laser nitriding

AU - Chan, Chi Wai

AU - Chang, Xianwen

AU - Bozorgzadeh, Mohammad Amin

AU - Smith, Graham C.

AU - Lee, Seunghwan

PY - 2020

Y1 - 2020

N2 - In this study, the idea of applying open-air laser nitriding to improve the microstructural and mechanical properties of beta Ti-45 at.% Nb alloy was demonstrated. Surface cracking after laser nitriding is one of the main reasons impeding direct translation of the laser nitriding technique from the laboratories to industries as cracks can be the weak points to initiate mechanical and corrosion failures in long-term usage. With proper selection of duty cycle (DC) between 40% (modulated mode) and 100% (continuous wave, CW mode) to control the laser energy input and laser-material-gas interaction time, the cracking problems of laser nitriding can be alleviated and even solved. A crack-free and uniformly gold-coloured nitrided surface was successfully obtained at the DC of 40% in this study. The morphology, microstructure, composition and mechanical properties of the nitrided samples were studied and analysed by optical microscopy (OM), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Vickers micro-hardness tests. The OM results indicated that minimum overlapping between the laser tracks would give desirable results to obtain the crack-free surface. The measurements from the SEM micrographs indicated the depth of the laser-nitrided areas ranged between 22 and 43 μm. The XRD findings showed that a clear conversion of the TiNb surface to a nitride as a result of laser nitriding was observed. The maximum hardness, as measured by the Vickers method in cross-sections, lie in the range of 780 to 870 HV after laser nitriding. To summarise, control of DC to obtain a crack free and quality surface via fiber laser nitriding in open air is a simpler and quicker approach in comparison with the conventional substrate preheating and nitrogen (N) dilution approaches. The single-parameter approach is more efficient than parameter optimisation via design of experiments (DOE) employed in conventional methods.

AB - In this study, the idea of applying open-air laser nitriding to improve the microstructural and mechanical properties of beta Ti-45 at.% Nb alloy was demonstrated. Surface cracking after laser nitriding is one of the main reasons impeding direct translation of the laser nitriding technique from the laboratories to industries as cracks can be the weak points to initiate mechanical and corrosion failures in long-term usage. With proper selection of duty cycle (DC) between 40% (modulated mode) and 100% (continuous wave, CW mode) to control the laser energy input and laser-material-gas interaction time, the cracking problems of laser nitriding can be alleviated and even solved. A crack-free and uniformly gold-coloured nitrided surface was successfully obtained at the DC of 40% in this study. The morphology, microstructure, composition and mechanical properties of the nitrided samples were studied and analysed by optical microscopy (OM), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Vickers micro-hardness tests. The OM results indicated that minimum overlapping between the laser tracks would give desirable results to obtain the crack-free surface. The measurements from the SEM micrographs indicated the depth of the laser-nitrided areas ranged between 22 and 43 μm. The XRD findings showed that a clear conversion of the TiNb surface to a nitride as a result of laser nitriding was observed. The maximum hardness, as measured by the Vickers method in cross-sections, lie in the range of 780 to 870 HV after laser nitriding. To summarise, control of DC to obtain a crack free and quality surface via fiber laser nitriding in open air is a simpler and quicker approach in comparison with the conventional substrate preheating and nitrogen (N) dilution approaches. The single-parameter approach is more efficient than parameter optimisation via design of experiments (DOE) employed in conventional methods.

KW - Beta Ti-Nb alloys

KW - Laser nitriding

KW - Fiber laser

KW - Titanium nitride (TiN)

KW - Orthopaedics

U2 - 10.1016/j.surfcoat.2019.125269

DO - 10.1016/j.surfcoat.2019.125269

M3 - Journal article

VL - 383

JO - Surface and Coatings Technology

JF - Surface and Coatings Technology

SN - 0257-8972

M1 - 125269

ER -