Lubricious silver tantalate films for extreme temperature applications

Stone, D. S.; Harbin, Samuel; Mohseni, H.; Mogonye, Jon-Erik; Scharf, Thomas; Muratore, Christopher; Voevodin, Andrey A.; Martini, Ashlie; Aouadi, Samir

doi:10.1016/j.surfcoat.2012.12.004

Cited by 66 publications

(38 citation statements)

References 24 publications

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“…In the case of NbN, the CoF against Si 3 N 4 counterface steadily reduced from 0.9 at RT to 0.52 at 750°C and XRD revealed that NbN coating was completely oxidised into monoclinic Nb 2 O 5 which has Magneli's phases [24]. The CoF of TaN against Si 3 N 4 counterface displayed a similar trend as seen in Figure 1 [25]. A mixed phase of orthorhombic Ta 2 O 5 and TaN was identified by XRD after tribotest at 750°C.…”

Section: Nitrides and Their Derivativessupporting

confidence: 59%

A State-of-the-art overview

Zhang

Dong

2014

Manufacturing Rev.

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Ever-increasing demand for severe work conditions, high-performance and long-life has been drivers for developing new low-friction and wear resistant coatings and surfaces for high temperature forming tools. This paper provides an overview on the recent development of coatings and modified surfaces to minimise friction and wear between contact surfaces in high-temperature working environments. This overview covers the major progresses in: (1) nanocomposite coatings based on transition metal nitrides and oxides, and the blending with solid lubricants such as silver and (2) multi-layered coatings with different combinations of hard and/or lubricating layers and duplex systems with solid lubricants on textured hard coatings and nanotubes. The challenges and future directions towards long-life and sustainable low-friction and wear-resistant coatings and surfaces for high-temperature forming tools are discussed.

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Section: Nitrides and Their Derivativessupporting

confidence: 59%

A State-of-the-art overview

Zhang

Dong

2014

Manufacturing Rev.

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“…Double metal oxides, including titanates, tungstates, molybdate, and vanadates, are effective high-temperature solid lubricants [8][9][10][11]. Among these double metal oxides, more attention has been paid to silver molybdate, which possesses a layer-like structure, because of its excellent lubrication performance, achieving low friction at high temperatures [2,[9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Friction and Wear Behavior of an Ag–Mo Co-Implanted GH4169 Alloy via Ion-Beam-Assisted Bombardment

et al. 2017

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Ag, Mo, and Ag-Mo were respectively implanted into GH4169 alloy substrates without heating via ion-beam-assisted bombardment technology (IBAB). In addition, the wear performance under low sliding speed and applied load were researched at room temperature (RT). A small amount silver molybdate phase could be detected on the surface of the co-implanted GH4169 alloy bombarded by a high-energy ion beam. The average friction coefficients under the steady wear state had almost no change at all. Compared with the un-implanted GH4169 alloys, the wear rate of the GH4169 alloys with co-implantation of Ag and Mo was reduced by 75%. A large amount of the silver molybdate phase could be generated due to the tribo-reaction on the worn surface during sliding. It benefits the formation of continuous oxide layers as lubrication and protected layers, leading to the change in the predominant wear mechanism from abrasion and adhesion wear to oxidation wear.

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“…[3][4][5][6] Very recently, silver tantalate (AgTaO 3 ) was reported to be a promising lubricant material at elevated temperatures. 7,8 The measured coefficient of friction (CoF) at 750 C was found to be as low as 0.04-0.06 in two recent studies conducted by our group. Additionally, transmission electron microscopy (TEM) revealed that the AgTaO 3 phase produced clusters of silver surrounded by Ta 2 O 5 near the surface, where the applied stress was presumed to attain its maximum values.…”

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confidence: 91%

“…Reconstruction of AgTaO 3 from the silver and Ta 2 O 5 phases from mechanical mixing during wear testing has also been hypothesized. 7 With increased normal force during testing, the diffusion and plowing of the silver from the surface increased, causing the coating to decrease in density and increase in porosity. MD modeling complemented the experimental results and supported the hypothesis that friction increased with load due to changes in the silver distribution and near-surface density.…”

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confidence: 99%

“…This behavior is different from that observed for AgTaO 3 under the same testing conditions where silver was primarily pushed to the edges of the wear track. 7 The incomplete coverage of silver in the wear track is likely the cause in the larger CoF on Ta 2 O 5 /Ag compared to AgTaO 3 . This is supported by the observation that Ta 2 O 5 , which is a much harder phase that does not shear easily, displayed a CoF of $0.5 under the same testing conditions.…”

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confidence: 99%

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Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

Stone

Gao

Chantharangsi

et al. 2014

Applied Physics Letters

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Silver tantalate (AgTaO 3 ) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application. V C 2014 AIP Publishing LLC. It is well established that high temperature working environments are still a major challenge for the tribology community. Oxidation of the commonly-used solid lubricants, such as MoS 2 and graphite, has hampered their use at elevated temperatures due to the degradation of material properties. 1 Solid lubricants that have been reported in the literature as well as used in industry when the temperature exceeds $300 C include noble metals, alkaline halides, Magn eli phases, and ternary oxides (also termed binary metal oxides).2 These systems usually exhibit friction coefficients in the range of 0.1-0.4, depending on the selected material, working temperature, and load. For more detailed information on the properties of these materials as high temperature solid lubricants, the reader is encouraged to refer to the following review articles. [3][4][5][6] Very recently, silver tantalate (AgTaO 3 ) was reported to be a promising lubricant material at elevated temperatures. 7,8 The measured coefficient of friction (CoF) at 750 C was found to be as low as 0.04-0.06 in two recent studies conducted by our group. Additionally, transmission electron microscopy (TEM) revealed that the AgTaO 3 phase produced clusters of silver surrounded by Ta 2 O 5 near the surface, where the applied stress was presumed to attain its maximum values. These features were reproduced in molecular dynamics (MD) simulations, 8,9 and results indicated that the lubricious nature of AgTaO 3 at high temperatures was enabled by the joint contributions of the hard Ta 2 O 5 phase and lubricious silver clusters in the shear-and temperature-induced surface layer. Theoretical and experimental cross-sectional images of the coatings in the wear track revealed that the presence of Ta 2 O 5 and silver increased dramatically closer to the interface whereas the remainder of the coating consisted primarily of AgTaO 3 with a very small amo...

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Lubricious silver tantalate films for extreme temperature applications

Cited by 66 publications

References 24 publications

A State-of-the-art overview

A State-of-the-art overview

Friction and Wear Behavior of an Ag–Mo Co-Implanted GH4169 Alloy via Ion-Beam-Assisted Bombardment

Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

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