Pilling-Bedworth ratio for oxidation of alloys

Xu, Chunhua; Gao, Wei

doi:10.1007/s100190050008

Cited by 345 publications

(112 citation statements)

References 4 publications

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“…Epitaxial strains in this case can be excluded based on our texture studies. Although it has been shown that volumetric differences due to oxide growth are not the unique mechanism of internal stress formation [1][2][3], they are still reported to be a relevant cause of growth stresses in oxide scales [67][68][69].…”

Section: Magnetitementioning

confidence: 99%

Effect of Substrate Grain Size on the Growth, Texture and Internal Stresses of Iron Oxide Scales Forming at 450 °C

et al. 2009

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The oxidation behavior of iron polycrystals and single crystals with (110) surface orientation was studied at 450°C. Energy-dispersive diffraction with synchrotron radiation provided in situ information regarding the evolution of stress gradients and fiber texture in the oxide scales. Within this low-temperature regime, grain boundaries caused the oxidation kinetics of polycrystalline iron to be more rapid than iron single crystals only during the first minutes of oxidation. Epitaxial growth of iron oxides occurred only on single crystal substrates during the initial oxidation. In situ stress analyses suggested that stress relief occurred invariably in the magnetite layer due to the formation of a fine-grained seam near the iron substrates. Above the magnetite and in the hematite layer, the growth stresses depend initially on volumetric strains and later on inner oxide formation and creep of the hematite.

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Section: Magnetitementioning

confidence: 99%

Effect of Substrate Grain Size on the Growth, Texture and Internal Stresses of Iron Oxide Scales Forming at 450 °C

et al. 2009

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“…Thus, the second, most likely, mechanism is the volumetric strain caused by differences in atomic volume between the first-formed grains of magnetite and wüstite. Although it has been shown that volumetric differences due to oxide growth are not the unique mechanism of internal stress formation [1][2][3], they are still reported to be a relevant cause of growth stresses in oxide scales [50][51][52]. However, iron is the rapidly diffusing specie through the magnetite/wüstite interface.…”

Section: Initial Stress Situationmentioning

confidence: 99%

Evolution of Microstructure and Internal Stresses in Multi-Phase Oxide Scales Grown on (110) Surfaces of Iron Single Crystals at 650 °C

et al. 2009

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The evolution of microstructure and growth stresses in oxide scales grown on a (110) iron single crystal surface at 650°C was studied by electron backscatter diffraction and in situ energy-dispersive diffraction with synchrotron radiation. Within this high temperature regime, the oxidation kinetics and scale microstructure were not significantly different from those encountered in the oxidation of ferrous polycrystals. Thus, epitaxial strains did not determine the stress state within the oxide scale. Relevant sources of growth stresses were inferred to be volumetric differences between the iron oxides in the early stages, and later, inner oxide formation, scale consumption as well as pore formation. These sources caused time-dependent stress cycles in magnetite and wüstite during oxidation. In the hematite layer stress cycles did not occur and creep appeared to be the predominant stress relieving mechanism. On cooling, the differences in thermal expansion caused residual stress gradients through the oxide scale.

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“…(i) The large volume expansion of Ti upon its oxidation measured by the Pilling-Bedworth ratio (PBR), which in the case of (rutile) TiO 2 /Ti is 1.73 [2,3] (for a value in excess of one, compressive stress will rapidly develop in the growing oxide scale-thus a high PBR value of 1.73 implies inherently large growth stresses in oxide layers on titanium and its alloys);…”

Section: Introductionmentioning

confidence: 99%

Surface modification of Ti–6Al–4V alloys using triode plasma oxidation treatments

Cassar

Wilson²,

Banfield

et al. 2012

Surface and Coatings Technology

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In this study, triode plasma oxidation (TPO) has been used to improve the tribological characteristics of Ti-6Al-4V. The effect of TPO on ball-on-plate reciprocating-sliding, impact, and micro-abrasion wear resistance of this alloy is investigated. Surface micro-profilometry, nano-/micro-indentation hardness testing, scratch-adhesion testing, scanning electron microscopy (SEM), atomic force microscopy (AFM), glancing-angle X-ray diffraction (GAXRD), and glow-discharge optical emission spectroscopy (GDOES) data is presented to corroborate the effects of the oxidation process. 'Traditional' thermal oxidation processes were used to benchmark this novel treatment. Following TPO treatment at 700°C for only 4 h, a hard (exceeding 11 GPa) and well-adhered oxide layer, composed of mixtures of the anatase and rutile polymorphs of TiO 2 , was formed at the surface of the Ti-alloy. This layer is accompanied by a much larger oxygen-solution strengthened zone which creates a gradual chemical and mechanical gradient from the hard oxide 'compound layer' into the ductile substrate core. The various wear testing methods employed revealed excellent wear resistance of the TPO-treated alloy-compared both to the untreated alloy and to conventional, thermally oxidised samples.

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Pilling-Bedworth ratio for oxidation of alloys

Cited by 345 publications

References 4 publications

Effect of Substrate Grain Size on the Growth, Texture and Internal Stresses of Iron Oxide Scales Forming at 450 °C

Effect of Substrate Grain Size on the Growth, Texture and Internal Stresses of Iron Oxide Scales Forming at 450 °C

Evolution of Microstructure and Internal Stresses in Multi-Phase Oxide Scales Grown on (110) Surfaces of Iron Single Crystals at 650 °C

Surface modification of Ti–6Al–4V alloys using triode plasma oxidation treatments

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