Structure Investigation of Titanium Metallization Coating Deposited onto AlN Ceramics Substrate by Means of Friction Surfacing Process

The article presents selected properties of a titanium metallization coating deposited on aluminum nitride (AlN) ceramics surface by means of the friction surfacing method. Its mechanism is based on the formation of a joint between the surface of an AlN ceramics substrate and a thin Ti coating, involving a kinetic energy of friction, which is directly converted into heat and delivered in a precisely defined quantity to the resulting joint. The largest effects on the final properties of the obtained coating include the high affinity of titanium for oxygen and nitrogen and a relatively high temperature for the deposition process. The titanium metallization coating was characterized in terms of surface stereometric structure, thickness, surface morphology, metallographic microstructural properties, and phase structure. The titanium coating has a thickness ranging from 3 to 7 μm. The phase structure of the coating surface (XPS investigated) is dominated by TiNxOy with the presence of TiOx, TiN, metallic Ti, and AlN. The phase structure deeper below the surface (XRD investigated) is dominated by metallic Ti with additional AlN particles originating from the ceramic substrate due to friction by titanium tools.

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Comparison of Mechanical and Microstructural Properties of as-Cast Al-Cu-Mg-Ag Alloys: Room Temperature vs. High Temperature

Crystals ◽

10.3390/cryst11111330 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1330

Author(s):

Muhammad Farzik Ijaz ◽

Mahmoud S. Soliman ◽

Ahmed S. Alasmari ◽

Adel T. Abbas ◽

Faraz Hussain Hashmi

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Mechanical Testing ◽

Tensile Testing ◽

Room Temperature ◽

Elevated Temperatures ◽

Microstructural Properties ◽

Testing Environments ◽

Mechanical And Microstructural Properties ◽

Mg Content

Unfolding the structure–property linkages between the mechanical performance and microstructural characteristics could be an attractive pathway to develop new single- and polycrystalline Al-based alloys to achieve ambitious high strength and fuel economy goals. A lot of polycrystalline as-cast Al-Cu-Mg-Ag alloy systems fabricated by conventional casting techniques have been reported to date. However, no one has reported a comparison of mechanical and microstructural properties that simultaneously incorporates the effects of both alloy chemistry and mechanical testing environments for the as-cast Al-Cu-Mg-Ag alloy systems. This preliminary prospective paper presents the examined experimental results of two alloys (denoted Alloy 1 and Alloy 2), with constant Cu content of ~3 wt.%, Cu/Mg ratios of 12.60 and 6.30, and a constant Ag of 0.65 wt.%, and correlates the synergistic comparison of mechanical properties at room and elevated temperatures. According to experimental results, the effect of the precipitation state and the mechanical properties showed strong dependence on the composition and testing environments for peak-aged, heat-treated specimens. In the room-temperature mechanical testing scenario, the higher Cu/Mg ratio alloy with Mg content of 0.23 wt.% (Alloy 1) possessed higher ultimate tensile strength when compared to the low Cu/Mg ratio with Mg content of 0.47 wt.% (Alloy 2). From phase constitution analysis, it is inferred that the increase in strength for Alloy 1 under room-temperature tensile testing is mainly ascribable to the small grain size and fine and uniform distribution of θ precipitates, which provided a barrier to slip by deaccelerating the dislocation movement in the room-temperature environment. Meanwhile, Alloy 2 showed significantly less degradation of mechanical strength under high-temperature tensile testing. Indeed, in most cases, low Cu/Mg ratios had a strong influence on the copious precipitation of thermally stable omega phase, which is known to be a major strengthening phase at elevated temperatures in the Al-Cu-Mg-Ag alloying system. Consequently, it is rationally suggested that in the high-temperature testing scenario, the improvement in mechanical and/or thermal stability in the case of the Alloy 2 specimen was mainly due to its compositional design.

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Calculation of magnetic suspension based on high-temperature superconductors for kinetic energy storage

Russian Electrical Engineering ◽

10.3103/s1068371212070061 ◽

2012 ◽

Vol 83 (7) ◽

pp. 385-388 ◽

Cited By ~ 5

Author(s):

Yu. V. Kulaev ◽

P. A. Kurbatov ◽

E. P. Kurbatova ◽

O. L. Polushchenko

Keyword(s):

High Temperature ◽

Energy Storage ◽

Kinetic Energy ◽

High Temperature Superconductors ◽

Magnetic Suspension

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Mechanical and microstructural properties of alkali-activated slag and slag + fly ash mortars exposed to high temperature

Construction and Building Materials ◽

10.1016/j.conbuildmat.2019.05.055 ◽

2019 ◽

Vol 217 ◽

pp. 50-61 ◽

Cited By ~ 15

Author(s):

Serhat Çelikten ◽

Mustafa Sarıdemir ◽

İbrahim Özgür Deneme

Keyword(s):

High Temperature ◽

Microstructural Properties ◽

Alkali Activated Slag ◽

Mechanical And Microstructural Properties ◽

Activated Slag ◽

Alkali Activated

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Cobalt addition effects on martensitic transformation and microstructural properties of high-temperature Cu–Al–Fe shape-memory alloys

Journal of Thermal Analysis and Calorimetry ◽

10.1007/s10973-015-4395-5 ◽

2015 ◽

Vol 120 (2) ◽

pp. 1227-1232 ◽

Cited By ~ 9

Author(s):

Koksal Yildiz ◽

Mediha Kök ◽

Fethi Dağdelen

Keyword(s):

High Temperature ◽

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Microstructural Properties ◽

Cobalt Addition

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Study on Heating Process of Dehumidifying Experiment in HTGR

Volume 1: Beyond Design Basis; Codes and Standards; Computational Fluid Dynamics (CFD); Decontamination and Decommissioning; Nuclear Fuel and Engineering; Nuclear Plant Engineering ◽

10.1115/icone2020-16358 ◽

2020 ◽

Author(s):

Kaiyue Shen ◽

Wei Zheng ◽

Shengchao Ma ◽

Huaqiang Yin ◽

Xuedong He ◽

...

Keyword(s):

High Temperature ◽

Kinetic Energy ◽

Thermal Energy ◽

Reactor Core ◽

Primary Circuit ◽

Heating Process ◽

Transfer Model ◽

Thermal Source ◽

Flow And Heat Transfer ◽

Selection Of

Abstract A large number of carbon materials are used in high temperature gas-cooled reactor (HTGR). As a kind of porous material, the carbon material contains a certain amount of moisture and other impurities. In order to reduce the corrosion of internal material in reactor core of HTGR, the initial core or post-accident core must be strictly heated and dehumidified. The current primary circuit heating mainly relies on the rotation of the primary pump to convert the kinetic energy into thermal energy. Obviously, the current scheme was flawed: (1) Due to the insufficient heat generated by rotation of the primary pump, the temperature rising process of the primary circuit is sluggish; (2) The rotation of the primary pump converts the kinetic energy into thermal energy of the helium, at the meantime, the primary circuit dissipates heat outward. For the above reasons, it is difficult to achieve the desired dehumidification temperature in the heating process. While in this paper, an additional thermal source will be added to the steam generator to heat the primary circuit in a new scheme. A proper flow and heat-transfer model of heating the primary circuit in high-temperature reactor was established based on software COMSOL Multiphysics. The numerical analysis of the primary circuit heating process provides rewarding guidance for the selection of the dehumidification scheme in HTGR.

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Test Evolution and Oil-Free Engine Experience of a High Temperature Foil Air Bearing Coating

Volume 5: Marine; Microturbines and Small Turbomachinery; Oil and Gas Applications; Structures and Dynamics, Parts A and B ◽

10.1115/gt2006-90572 ◽

2006 ◽

Cited By ~ 22

Author(s):

Daniel Lubell ◽

Christopher DellaCorte ◽

Malcolm Stanford

Keyword(s):

High Temperature ◽

Gas Turbines ◽

Solid Lubricants ◽

Deposition Process ◽

Air Bearing ◽

Free Gas ◽

Foil Bearings ◽

Start Up ◽

High Temperature Operation

During the start-up and shut-down of a turbomachine supported on compliant foil bearings, before the bearings have full development of the hydrodynamic gas film, sliding occurs between the rotor and the bearing foils. Traditional solid lubricants (e.g., graphite, Teflon®) readily solve this problem at low temperature. High temperature operation, however, has been a key obstacle. Without a suitable high temperature coating, foil air bearing use is limited to about 300°C (570°F). In oil-free gas turbines, a hot section bearing presents a very aggressive environment for these coatings. A NASA developed coating, PS304, represents one tribological approach to this challenge. In this paper, the use of PS304 as a rotor coating operating against a hot foil gas bearing is reviewed and discussed. During the course of several long term, high cycle, engine tests, which included two coating related failures, the PS304 technology evolved and improved. For instance, a post deposition thermal treatment to improve dimensional stability, and improvements to the deposition process to enhance strength resulted from the engine evaluations. Largely because of this work, the bearing/coating combination has been successfully demonstrated at over 500°C (930°F) in an oil-free gas turbine for over 2500 hours and 2900 start-stop cycles without damage or loss of performance when properly applied. Ongoing testing at Glenn Research Center as part of a long term program is over 3500 hours and 150 cycles.

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