Oxidation‐led decomposition of hexagonal boron nitride coatings on alloy substrates at 900°C

Ti‐6Al‐4V

Research output: Contribution to journalArticle

Abstract

Hexagonal boron nitride (h‐BN) coatings on Ti‐6Al‐4V substrates undergo complete decomposition in air at 900 °C. This fate is similar to that of this ceramic material on chromia‐former alloys, and unlike that of a mass of powder treated in isolation. As the ceramic and alloy oxidize concurrently, outwardly diffusing aluminum (III) ions but not the predominant titanium (IV) ions react with the boron trioxide that forms around the h‐BN basal plane peripheries. Resultant aluminum borate is incorporated into the growing scale and the boron trioxide diffusion barrier is depleted. By this mechanism, the oxidation of h‐BN is maintained at an enhanced rate, until both this material and its oxide completely decompose. Liberated nitrogen from the oxidation of h‐BN can enter the underlying scale as a randomly distributed solute in rutile solid solution. The post‐coating oxide‐atmosphere interface comprises elongated aluminum borate crystallites protruding through at the boundaries between 3–5 at% nitrogen‐doped rutile grains. It differs significantly from that of oxidized, uncoated Ti‐6Al‐4V, which is occupied by a thin α‐alumina layer atop rutile. This interface does not change with an additional 72 h of heat‐treatment.
Original languageEnglish
Pages (from-to)1617-1632
Number of pages16
JournalMaterials and Corrosion-Werkstoffe und Korrosion
Volume70
Issue number9
Early online date15 Apr 2019
DOIs
Publication statusPublished - 30 Sep 2019

Fingerprint

Boron nitride
boron
coating
Aluminum
decomposition
Decomposition
substrate
Coatings
Borates
Boron
Substrates
rutile
borate
aluminum
Ions
ceramics
Oxidation
Diffusion barriers
Aluminum Oxide
Ceramic materials

Keywords

  • ceramic platelets
  • decomposition reaction
  • high temperature oxidation
  • metal forming
  • titanium alloy

Cite this

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title = "Oxidation‐led decomposition of hexagonal boron nitride coatings on alloy substrates at 900°C: Ti‐6Al‐4V",
abstract = "Hexagonal boron nitride (h‐BN) coatings on Ti‐6Al‐4V substrates undergo complete decomposition in air at 900 °C. This fate is similar to that of this ceramic material on chromia‐former alloys, and unlike that of a mass of powder treated in isolation. As the ceramic and alloy oxidize concurrently, outwardly diffusing aluminum (III) ions but not the predominant titanium (IV) ions react with the boron trioxide that forms around the h‐BN basal plane peripheries. Resultant aluminum borate is incorporated into the growing scale and the boron trioxide diffusion barrier is depleted. By this mechanism, the oxidation of h‐BN is maintained at an enhanced rate, until both this material and its oxide completely decompose. Liberated nitrogen from the oxidation of h‐BN can enter the underlying scale as a randomly distributed solute in rutile solid solution. The post‐coating oxide‐atmosphere interface comprises elongated aluminum borate crystallites protruding through at the boundaries between 3–5 at{\%} nitrogen‐doped rutile grains. It differs significantly from that of oxidized, uncoated Ti‐6Al‐4V, which is occupied by a thin α‐alumina layer atop rutile. This interface does not change with an additional 72 h of heat‐treatment.",
keywords = "ceramic platelets, decomposition reaction, high temperature oxidation, metal forming, titanium alloy",
author = "Christopher Fleming",
year = "2019",
month = "9",
day = "30",
doi = "10.1002/maco.201810706",
language = "English",
volume = "70",
pages = "1617--1632",
journal = "Materials and Corrosion-Werkstoffe und Korrosion",
issn = "0947-5117",
number = "9",

}

TY - JOUR

T1 - Oxidation‐led decomposition of hexagonal boron nitride coatings on alloy substrates at 900°C

T2 - Ti‐6Al‐4V

AU - Fleming, Christopher

PY - 2019/9/30

Y1 - 2019/9/30

N2 - Hexagonal boron nitride (h‐BN) coatings on Ti‐6Al‐4V substrates undergo complete decomposition in air at 900 °C. This fate is similar to that of this ceramic material on chromia‐former alloys, and unlike that of a mass of powder treated in isolation. As the ceramic and alloy oxidize concurrently, outwardly diffusing aluminum (III) ions but not the predominant titanium (IV) ions react with the boron trioxide that forms around the h‐BN basal plane peripheries. Resultant aluminum borate is incorporated into the growing scale and the boron trioxide diffusion barrier is depleted. By this mechanism, the oxidation of h‐BN is maintained at an enhanced rate, until both this material and its oxide completely decompose. Liberated nitrogen from the oxidation of h‐BN can enter the underlying scale as a randomly distributed solute in rutile solid solution. The post‐coating oxide‐atmosphere interface comprises elongated aluminum borate crystallites protruding through at the boundaries between 3–5 at% nitrogen‐doped rutile grains. It differs significantly from that of oxidized, uncoated Ti‐6Al‐4V, which is occupied by a thin α‐alumina layer atop rutile. This interface does not change with an additional 72 h of heat‐treatment.

AB - Hexagonal boron nitride (h‐BN) coatings on Ti‐6Al‐4V substrates undergo complete decomposition in air at 900 °C. This fate is similar to that of this ceramic material on chromia‐former alloys, and unlike that of a mass of powder treated in isolation. As the ceramic and alloy oxidize concurrently, outwardly diffusing aluminum (III) ions but not the predominant titanium (IV) ions react with the boron trioxide that forms around the h‐BN basal plane peripheries. Resultant aluminum borate is incorporated into the growing scale and the boron trioxide diffusion barrier is depleted. By this mechanism, the oxidation of h‐BN is maintained at an enhanced rate, until both this material and its oxide completely decompose. Liberated nitrogen from the oxidation of h‐BN can enter the underlying scale as a randomly distributed solute in rutile solid solution. The post‐coating oxide‐atmosphere interface comprises elongated aluminum borate crystallites protruding through at the boundaries between 3–5 at% nitrogen‐doped rutile grains. It differs significantly from that of oxidized, uncoated Ti‐6Al‐4V, which is occupied by a thin α‐alumina layer atop rutile. This interface does not change with an additional 72 h of heat‐treatment.

KW - ceramic platelets

KW - decomposition reaction

KW - high temperature oxidation

KW - metal forming

KW - titanium alloy

UR - https://onlinelibrary.wiley.com/journal/15214176

U2 - 10.1002/maco.201810706

DO - 10.1002/maco.201810706

M3 - Article

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EP - 1632

JO - Materials and Corrosion-Werkstoffe und Korrosion

JF - Materials and Corrosion-Werkstoffe und Korrosion

SN - 0947-5117

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ER -