Search results for "Thermal bar"
showing 10 items of 11 documents
Interannual variability of circulation under spring ice in a boreal lake
2014
A small range (, 1uC) of under-ice water temperature is shown to result in remarkably different circulation regimes under spring ice in a deep, oligotrophic boreal lake. With the water column at , 4uC, melting of snow led to deepening vertical convection before ice break and a final depth of convection inversely correlated with earlier deep-water temperature. We attribute that to the nonlinear dependence of water density on temperature, albeit further affected by stochastic weather factors. In four of nine study years, convection led to complete under-ice overturn of the lake, indicating that this may not be uncommon in similar lakes with steep topography. River inflow and more intensive wa…
Thermophysical-Property-Based Selection of Tool Protective Coatings for Dry Machining of Steels
2003
A method is proposed for determining the optimum cutting conditions in dry turning of carbon and stainless steels using multilayer coated tools for physical criteria such as the maximum temperature of a cutting tool or maximum heat flux. The modified thermal number describing the tool-chip behavior, is introduced. The correlation between the thermal number and the average tool-chip interface temperature and frictional heat flux is examined for both flat-faced and grooved rake configurations. Although not shown here directly, the thermal barrier effect observed for multilayer coatings with an intermediate Al2O3 layer increases the heat partition to the chip at substantially reduced cutting t…
Influence of Anodic and Thermal Barrier Layers on Physicochemical Behavior of Anodic TiO2 Nanotubes
2011
Electrochemical and photo-electrochemical behavior of self-organized TiO2 nanotubes formed in organic solvents have been studied by taking into account the formation of new barrier layers beneath nanotubes either due to the anodic polarization in aqueous solutions or air exposure during high temperature annealing. It has been shown that before annealing, electrochemical and photoelectrochemical answers are dominantly controlled by the physicochemical properties of the anodic barrier layer. Annealing in air at sufficiently high temperatures changes the initial amorphous structure of as-prepared nanotubes and forms a new oxide layer below them due to thermal oxidation of underneath titanium. …
Experimental investigation of the cutting temperature when turning with coated indexable inserts
1999
Abstract This paper deals with an experimental investigation into the different factors which influence the temperature which occur at the coating/substrate–chip interface when machining a medium carbon steel and an austenitic stainless steel. Both flat-faced and grooved inserts coated with TiC, TiC/TiN and TiC/Al 2 O 3 /TiN were used. A standard K-type thermocouple embedded in the workpiece was used to convert measured efms to the interfacial temperature. Some optimal coating structures for high speed machining of these steels corresponding to the minimum interface temperature were selected. In particular, it was observed that by the proper selection of the thermal properties of the coatin…
Erosion Behavior of PS-PVD Thermal Barrier Coatings and the Effect of Composite Coating (PS-PVD + APS) Thickness
2020
In this work, feather-column 7YSZ thermal barrier coatings (TBCs) were prepared by plasma spray-physical vapor deposition (PS-PVD). The anti-particle erosion test was carried out at room temperature to study the erosion behavior and failure mechanism of PS-PVD TBCs. The results showed that the particle erosion process of the PS-PVD TBCs experienced three stages of high-rate, medium-rate and slow-rate erosion. In order to improve the particle erosion resistance of the PS-PVD TBCs, different thicknesses of dense-layered coatings were prepared on the surface of the PS-PVD TBCs by air plasma spraying (APS). The effect of dense-layered thickness on the erosion behaviour of PS-PVD TBCs was discus…
Oxidation behavior of γ-TiAl coated with zirconia thermal barriers
2002
Abstract The applicability of the thermal barrier coating concept, which is an established concept for Ni-base alloys, was investigated for the first time for γ-TiAl. As potential bond coats, the following surface treatments were applied: Al-diffusion coating, Al-diffusion coating combined with short term pre-oxidation in air, short term pre-oxidation in oxygen of a rough surface finish γ-TiAl sample without aluminide coating. For the purpose of lowering the temperature of the γ-TiAl substrate surface, and thus, to prolong the life time, a zirconia thermal barrier coating (TBC) was applied on top of the above-mentioned modified TiAl surfaces. Oxidation resistance of the modified γ-TiAl allo…
Microstructure and mechanical properties of plasma spraying coatings from YSZ feedstocks comprising nano-and submicron-sized particles
2015
Atmospheric plasma spraying (APS) is an attractive technique to obtain nanostructured coatings due to its versatility, simplicity and relatively low cost. However, nanoparticles cannot be fed into the plasma using conventional feeding systems, due to their low mass and poor flowability, and must be adequately reconstituted into sprayable micrometric agglomerates. In this work, nanostructured and submicron/nanostiuctured powders of yttria-stabilised zirconia (YSZ) were deposited using APS, with a view to obtaining high-performance thermal bather coatings (IBC). All powders were reconstituted by spray-drying from different solid loading suspensions, followed by a thermal treatment of the spra…
Properties of atomic layer deposited nanolaminates of zirconium and cobalt oxides
2018
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Multiple Crack Localization and Debonding Mechanisms for Thin Thermal Coating Films
2020
Experimental tests, carried out on small scale alloy specimens covered on one side with a thin thermal coating, have shown complex failure mechanisms. The failure mechanisms observed are due to the competition between two fracture mechanisms. The two mechanisms are: (i) Vertical tensile coating surface cracks and (ii) debonding shear decohesion mechanisms along the interface between the coating and the substrate. The present paper analyzes the mechanical problem of the nonlinear behavior thin film on a stiff substrate adopting a computational approach. Namely, incremental 2D nonlinear finite element simulations. The stiff superalloy substrate is modeled as a thermo-elastic material. The coa…
Porous architecture and thermal properties of thermal barrier coatings deposited by suspension plasma spray
2020
Abstract Besides the intrinsic low heat transfer capability of material, the thermal insulation property of thermal barrier coatings (TBCs) also relies on their microstructures. For better understanding the relationship between process parameters, porous architecture, and thermal properties of coatings, YSZ coatings were firstly manufactured by suspension plasma spray (SPS). Afterwards their total porosities were characterized by using the technique of X-ray transmission, the nano/submicro pores in those coatings were detected with Ultra-Small Angle X-ray Scattering (USAXS), and the thermal properties of coatings were measured using the laser flash method. The results indicated that: i) the…