A two-step laser-sustained plasma nitriding process for deep-case hardening of commercially pure titanium

Amar M. Kamat, Stephen M. Copley, Judith A. Todd

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A two-step, laser-sustained plasma (LSP) process was developed to form deep, hard, nitrided cases on commercially pure titanium. A laser-sustained plasma is plasma generated in a gaseous atmosphere that can be sustained indefinitely by the laser beam away from any potentially interacting surface. The first step utilized a nitrogen LSP associated with a defocused CO2 laser beam in pure nitrogen gas flow to melt and nitride the titanium surface. The second step used an argon LSP to remelt and refine the nitrided layer. Twenty experimental cases with varying nitriding and remelting speeds were studied. Optical and scanning electron microscopy, energy dispersive spectroscopy, optical profilometry, and x-ray diffraction were used to characterize the remelted nitrided layer. An analytical moving heat source solution was used to model the heat transfer in the melt pool during the nitriding and remelting processes. The mass flux of nitrogen into the melt pool and the efficiency of nitrogen intake were estimated. The remelting treatment was found to eliminate the surface cracks formed during nitriding, decrease the surface roughness of the nitrided trail, homogenize the hardened surface layer, and refine the microstructure. The microstructures and hardness of the nitrided layers could be tailored by changing the combination of LSP nitriding and remelting scan speeds. Case depths of up to 0.8 mm and average case hardness values in the range of 475–729 HV0.3 were achieved in this study.

Original languageEnglish (US)
Pages (from-to)82-95
Number of pages14
JournalSurface and Coatings Technology
Volume313
DOIs
StatePublished - Mar 15 2017

Fingerprint

Case hardening
nitriding
Nitriding
Titanium
hardening
Remelting
titanium
Plasmas
Lasers
Nitrogen
melting
lasers
nitrogen
Laser beams
hardness
Hardness
laser beams
Argon lasers
argon lasers
nitrogen lasers

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

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title = "A two-step laser-sustained plasma nitriding process for deep-case hardening of commercially pure titanium",
abstract = "A two-step, laser-sustained plasma (LSP) process was developed to form deep, hard, nitrided cases on commercially pure titanium. A laser-sustained plasma is plasma generated in a gaseous atmosphere that can be sustained indefinitely by the laser beam away from any potentially interacting surface. The first step utilized a nitrogen LSP associated with a defocused CO2 laser beam in pure nitrogen gas flow to melt and nitride the titanium surface. The second step used an argon LSP to remelt and refine the nitrided layer. Twenty experimental cases with varying nitriding and remelting speeds were studied. Optical and scanning electron microscopy, energy dispersive spectroscopy, optical profilometry, and x-ray diffraction were used to characterize the remelted nitrided layer. An analytical moving heat source solution was used to model the heat transfer in the melt pool during the nitriding and remelting processes. The mass flux of nitrogen into the melt pool and the efficiency of nitrogen intake were estimated. The remelting treatment was found to eliminate the surface cracks formed during nitriding, decrease the surface roughness of the nitrided trail, homogenize the hardened surface layer, and refine the microstructure. The microstructures and hardness of the nitrided layers could be tailored by changing the combination of LSP nitriding and remelting scan speeds. Case depths of up to 0.8 mm and average case hardness values in the range of 475–729 HV0.3 were achieved in this study.",
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A two-step laser-sustained plasma nitriding process for deep-case hardening of commercially pure titanium. / Kamat, Amar M.; Copley, Stephen M.; Todd, Judith A.

In: Surface and Coatings Technology, Vol. 313, 15.03.2017, p. 82-95.

Research output: Contribution to journalArticle

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AB - A two-step, laser-sustained plasma (LSP) process was developed to form deep, hard, nitrided cases on commercially pure titanium. A laser-sustained plasma is plasma generated in a gaseous atmosphere that can be sustained indefinitely by the laser beam away from any potentially interacting surface. The first step utilized a nitrogen LSP associated with a defocused CO2 laser beam in pure nitrogen gas flow to melt and nitride the titanium surface. The second step used an argon LSP to remelt and refine the nitrided layer. Twenty experimental cases with varying nitriding and remelting speeds were studied. Optical and scanning electron microscopy, energy dispersive spectroscopy, optical profilometry, and x-ray diffraction were used to characterize the remelted nitrided layer. An analytical moving heat source solution was used to model the heat transfer in the melt pool during the nitriding and remelting processes. The mass flux of nitrogen into the melt pool and the efficiency of nitrogen intake were estimated. The remelting treatment was found to eliminate the surface cracks formed during nitriding, decrease the surface roughness of the nitrided trail, homogenize the hardened surface layer, and refine the microstructure. The microstructures and hardness of the nitrided layers could be tailored by changing the combination of LSP nitriding and remelting scan speeds. Case depths of up to 0.8 mm and average case hardness values in the range of 475–729 HV0.3 were achieved in this study.

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