Gaseous surface hardening of Ti-6Al-4V fabricated by selective laser melting

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Abstract

The present work investigates the response of different gaseous thermochemical treatments on selective laser melted (SLM) Ti-6Al-4V. The resulting microstructures after thermochemical treatment were investigated with X-ray diffraction, light optical microscopy, scanning electron microscopy and Vickers-microhardness indentation. Nitriding, performed at 1000–1050 °C resulted in a diffusion zone of nitrogen in solid solution and surface compound layers consisting of TiN (and Ti2N at 1000 °C). Below the compound layer Al-enrichment of the α-zone was observed. Carbo-oxidising in a CO atmosphere at 1000–1050 °C resulted in deep diffusion zones and thick compound layers of the ternary compound TiC1-xOx. Both surface hardness and layer depth were found to increase with temperature and treatment time. Chemically controlled carbo-oxidising, applying the gas redox system CO-CO2, was performed at temperatures in the range 850–1050 °C, resulting in carbo-oxides and formation of oxides with increasing Ti:O ratio with increasing temperatures (rutile and Magnéli phases). Nitriding followed by (carbo-)oxidising treatment resulted in higher surface hardness owing to the formation of mixed interstitial compounds TiC1-x-yNxOy in the compound layer. The compound layer grew into the Al-rich zone as elongated structures.

The improvement of wear by nitriding, carbo-oxidising and duplex nitriding/(carbo-)oxidising on SLM Ti-6Al-4V was evaluated by dry sliding wear testing. Lowering of the wear volume by up to a factor of 450 compared to an annealed reference sample was realised. Carbo-oxidising in CO at 1000 °C offered the best wear resistance and resulted in a lowering of the friction coefficient, averaging μ = 0.22, compared to μ = 0.45 for an annealed reference sample.
Original languageEnglish
Article number125278
JournalSurface and Coatings Technology
Volume383
Number of pages13
ISSN0257-8972
DOIs
Publication statusPublished - 2020

Keywords

  • Surface hardening
  • Ti-6Al-4V
  • Selective laser melting
  • Additive manufacturing
  • Microstructure
  • Wear

Cite this

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title = "Gaseous surface hardening of Ti-6Al-4V fabricated by selective laser melting",
abstract = "The present work investigates the response of different gaseous thermochemical treatments on selective laser melted (SLM) Ti-6Al-4V. The resulting microstructures after thermochemical treatment were investigated with X-ray diffraction, light optical microscopy, scanning electron microscopy and Vickers-microhardness indentation. Nitriding, performed at 1000–1050 °C resulted in a diffusion zone of nitrogen in solid solution and surface compound layers consisting of TiN (and Ti2N at 1000 °C). Below the compound layer Al-enrichment of the α-zone was observed. Carbo-oxidising in a CO atmosphere at 1000–1050 °C resulted in deep diffusion zones and thick compound layers of the ternary compound TiC1-xOx. Both surface hardness and layer depth were found to increase with temperature and treatment time. Chemically controlled carbo-oxidising, applying the gas redox system CO-CO2, was performed at temperatures in the range 850–1050 °C, resulting in carbo-oxides and formation of oxides with increasing Ti:O ratio with increasing temperatures (rutile and Magn{\'e}li phases). Nitriding followed by (carbo-)oxidising treatment resulted in higher surface hardness owing to the formation of mixed interstitial compounds TiC1-x-yNxOy in the compound layer. The compound layer grew into the Al-rich zone as elongated structures.The improvement of wear by nitriding, carbo-oxidising and duplex nitriding/(carbo-)oxidising on SLM Ti-6Al-4V was evaluated by dry sliding wear testing. Lowering of the wear volume by up to a factor of 450 compared to an annealed reference sample was realised. Carbo-oxidising in CO at 1000 °C offered the best wear resistance and resulted in a lowering of the friction coefficient, averaging μ = 0.22, compared to μ = 0.45 for an annealed reference sample.",
keywords = "Surface hardening, Ti-6Al-4V, Selective laser melting, Additive manufacturing, Microstructure, Wear",
author = "Valente, {Emilie H.} and Jellesen, {Morten S.} and Somers, {Marcel A. J.} and Christiansen, {Thomas L.}",
year = "2020",
doi = "10.1016/j.surfcoat.2019.125278",
language = "English",
volume = "383",
journal = "Surface and Coatings Technology",
issn = "0257-8972",
publisher = "Elsevier",

}

TY - JOUR

T1 - Gaseous surface hardening of Ti-6Al-4V fabricated by selective laser melting

AU - Valente, Emilie H.

AU - Jellesen, Morten S.

AU - Somers, Marcel A. J.

AU - Christiansen, Thomas L.

PY - 2020

Y1 - 2020

N2 - The present work investigates the response of different gaseous thermochemical treatments on selective laser melted (SLM) Ti-6Al-4V. The resulting microstructures after thermochemical treatment were investigated with X-ray diffraction, light optical microscopy, scanning electron microscopy and Vickers-microhardness indentation. Nitriding, performed at 1000–1050 °C resulted in a diffusion zone of nitrogen in solid solution and surface compound layers consisting of TiN (and Ti2N at 1000 °C). Below the compound layer Al-enrichment of the α-zone was observed. Carbo-oxidising in a CO atmosphere at 1000–1050 °C resulted in deep diffusion zones and thick compound layers of the ternary compound TiC1-xOx. Both surface hardness and layer depth were found to increase with temperature and treatment time. Chemically controlled carbo-oxidising, applying the gas redox system CO-CO2, was performed at temperatures in the range 850–1050 °C, resulting in carbo-oxides and formation of oxides with increasing Ti:O ratio with increasing temperatures (rutile and Magnéli phases). Nitriding followed by (carbo-)oxidising treatment resulted in higher surface hardness owing to the formation of mixed interstitial compounds TiC1-x-yNxOy in the compound layer. The compound layer grew into the Al-rich zone as elongated structures.The improvement of wear by nitriding, carbo-oxidising and duplex nitriding/(carbo-)oxidising on SLM Ti-6Al-4V was evaluated by dry sliding wear testing. Lowering of the wear volume by up to a factor of 450 compared to an annealed reference sample was realised. Carbo-oxidising in CO at 1000 °C offered the best wear resistance and resulted in a lowering of the friction coefficient, averaging μ = 0.22, compared to μ = 0.45 for an annealed reference sample.

AB - The present work investigates the response of different gaseous thermochemical treatments on selective laser melted (SLM) Ti-6Al-4V. The resulting microstructures after thermochemical treatment were investigated with X-ray diffraction, light optical microscopy, scanning electron microscopy and Vickers-microhardness indentation. Nitriding, performed at 1000–1050 °C resulted in a diffusion zone of nitrogen in solid solution and surface compound layers consisting of TiN (and Ti2N at 1000 °C). Below the compound layer Al-enrichment of the α-zone was observed. Carbo-oxidising in a CO atmosphere at 1000–1050 °C resulted in deep diffusion zones and thick compound layers of the ternary compound TiC1-xOx. Both surface hardness and layer depth were found to increase with temperature and treatment time. Chemically controlled carbo-oxidising, applying the gas redox system CO-CO2, was performed at temperatures in the range 850–1050 °C, resulting in carbo-oxides and formation of oxides with increasing Ti:O ratio with increasing temperatures (rutile and Magnéli phases). Nitriding followed by (carbo-)oxidising treatment resulted in higher surface hardness owing to the formation of mixed interstitial compounds TiC1-x-yNxOy in the compound layer. The compound layer grew into the Al-rich zone as elongated structures.The improvement of wear by nitriding, carbo-oxidising and duplex nitriding/(carbo-)oxidising on SLM Ti-6Al-4V was evaluated by dry sliding wear testing. Lowering of the wear volume by up to a factor of 450 compared to an annealed reference sample was realised. Carbo-oxidising in CO at 1000 °C offered the best wear resistance and resulted in a lowering of the friction coefficient, averaging μ = 0.22, compared to μ = 0.45 for an annealed reference sample.

KW - Surface hardening

KW - Ti-6Al-4V

KW - Selective laser melting

KW - Additive manufacturing

KW - Microstructure

KW - Wear

U2 - 10.1016/j.surfcoat.2019.125278

DO - 10.1016/j.surfcoat.2019.125278

M3 - Journal article

VL - 383

JO - Surface and Coatings Technology

JF - Surface and Coatings Technology

SN - 0257-8972

M1 - 125278

ER -