Evaluation of DLC Coatings for High-Temperature Foil Bearing Applications

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Said Jahanmir ◽  
Hooshang Heshmat ◽  
Crystal Heshmat
Keyword(s):  
Carbon Film ◽  
Dlc Coatings ◽  
Foil Bearings ◽  
Dlc Coating ◽  
Foil Bearing ◽  
Flat Disk ◽  
Wide Range ◽  
Diamondlike Carbon ◽  
Powder Lubrication ◽  
Foil Thrust Bearing

Diamondlike carbon (DLC) coatings, particularly in the hydrogenated form, provide extremely low coefficients of friction in concentrated contacts. The objective of this investigation was to evaluate the performance of DLC coatings for potential application in foil bearings. Since in some applications the bearings experience a wide range of temperatures, tribological tests were performed using a single foil thrust bearing in contact with a rotating flat disk up to 500°C. The coatings deposited on the disks consisted of a hydrogenated diamondlike carbon film (H-DLC), a nonhydrogenated DLC, and a thin dense chrome deposited by the Electrolyzing™ process. The top foil pads were coated with a tungsten disulfide based solid lubricant (Korolon™ 900). All three disk coatings provided excellent performance at room temperature. However, the H-DLC coating proved to be unacceptable at 300°C due to lack of hydrodynamic lift, albeit the very low coefficient of friction when the foil pad and the disk were in contact during stop-start cycles. This phenomenon is explained by considering the effect of atmospheric moisture on the tribological behavior of H-DLC and using the quasihydrodynamic theory of powder lubrication.

Evaluation of DLC Coatings for Foil Bearing Applications

2007 ◽  
Author(s):  
Said Jahanmir ◽  
Hooshang Heshmat ◽  
Crystal Heshmat ◽  
Osman Eryilmaz ◽  
Ali Erdemir
Keyword(s):  
Room Temperature ◽  
Excellent Performance ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Foil Bearings ◽  
Dlc Coating ◽  
Foil Bearing ◽  
Free Air ◽  
Flat Disk ◽  
Important Design

A critical component in oil-free air foil bearings is the tribological coating system that must be used on the journal/runner and the foil pads to ensure reliable operation during transient periods and start-stop cycles. The purpose of the present investigation was to evaluate the performance characteristics of hydrogenated diamond like carbon coatings (H-DLC) for foil bearing applications. Tribological tests were performed using a single thrust foil bearing in contact with a rotating flat disk at room temperature. While the performance of H-DLC coating on the foils tested against disks coated with MiTi® Korolon™ 900 was acceptable, the reverse coating combination provided an excellent performance. Although the H-DLC film had suffered some wear along narrow scratches, both coatings survived the 500 start/stop cycles. The liftoff speed, which is an important design parameter, was less than 1,000 rpm, much lower than uncoated foil and disk combination. It is, therefore, concluded that the combination of H-DLC foil coating with the Korolon™ 900 coating on the disk will provide excellent performance for foil bearing applications at room temperature.

Fracture toughness of diamondlike carbon coatings

1999 ◽  
Vol 14 (5) ◽  
pp. 2173-2180 ◽  
Author(s):  
M. Nastasi ◽  
P. Kodali ◽  
K. C. Walter ◽  
J. D. Embury ◽  
R. Raj ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Crack Length ◽  
Total Work ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Si Substrates ◽  
Dlc Coating ◽  
Diamondlike Carbon ◽  
Radial Cracks ◽  
Work Of Fracture

The fracture behavior of diamondlike carbon (DLC) coatings on Si substrates has been examined using microindentation. The presence of DLC coatings reduces the radial crack length to less than one-half the crack length observed in uncoated Si at the same indenter load. A total work of fracture analysis of the radial cracks formed in the DLC-coating/Si-substrate system gives 10.1 MPa m1/2 as the average fracture toughness for DLC alone. A bond-breaking calculation for DLC suggests that the elastic limit fracture toughness should be 1.5 MPa (m)1/2. The higher value obtained from experiment and total work analysis suggests that plastic work and/or a tortuous path crack evolution occurred during DLC fracture process.

Improved adhesion of diamondlike coatings using shallow carbon implantation

2000 ◽  
Vol 15 (3) ◽  
pp. 590-592 ◽  
Author(s):  
Gerard W. Malaczynski ◽  
Alaa A. Elmoursi ◽  
Chi H. Leung ◽  
Aboud H. Hamdi ◽  
Albert B. Campbell
Keyword(s):  
Silicon Content ◽  
Carbon Matrix ◽  
Metal Carbides ◽  
Cohesion Strength ◽  
Subsequent Growth ◽  
Dlc Coatings ◽  
Dlc Coating ◽  
Diamondlike Carbon ◽  
Plasma Immersion Ion Implantation ◽  
Implantation Profile

A surface layer of metal carbides provides an excellent interface to achieve a highly adherent diamondlike carbon (DLC) coating. A plasma immersion ion implantation (PIII)-based procedure is described, which delivers a high retained dose of implanted carbon at the surface of aluminum alloys. A shallow implantation profile, followed by argon sputter cleaning and continued until a saturated carbon matrix is brought to the surface, provides an excellent interface for subsequent growth of DLC. At a carbon retained dose above 1018 atoms/cm2 the DLC adhesion exceeds the coating's cohesion strength. Regardless of the silicon content in the aluminum, the coating produced by this method required tensile strengths typically exceeding 140 MPa to separate an epoxy-coated stud from the coating in a standard pull test. Improved DLC adhesion was also observed on chromium and titanium. The reported tensile strength is believed to substantially exceed performance of DLC coatings produced by any other method.

Application of Materials on Foil Thrust Bearings for Micro Turbines

2011 ◽  
Vol 201-203 ◽  
pp. 2759-2762
Author(s):  
Quan Zhou ◽  
Yu Hou ◽  
Ru Gang Chen
Keyword(s):  
Thrust Bearing ◽  
Load Capacity ◽  
Bearing Surface ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Soft Surface ◽  
Static Part ◽  
Micro Turbine ◽  
Foil Thrust Bearing

Foil bearing that has a soft surface is a kind of air bearing. The performances of foil bearings are greatly affected by the materials of bearing surface, which is called foil element. In order to estimate the performance of foil bearings, two kinds of foil thrust bearings that are made of different materials respectively were tested in a micro turbine system, which contains rotation part and static part. Load capacity and stability of these foil thrust bearings were investigated in experiments. The results show that bearing which contains rubber has higher load capacity and bearing which contains copper foil has higher stability. According to the work in this paper, applications with different requirements can adopt suitable foil thrust bearing.

Effects of wedge curvature on performances of foil thrust bearing and the profile design in compressor system

2020 ◽  
pp. 135065012097552
Author(s):  
Hao Li ◽  
Haipeng Geng ◽  
Lei Qi ◽  
Lu Gan
Keyword(s):  
Reynolds Equation ◽  
Thrust Bearing ◽  
Dynamic Performance ◽  
Testing System ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Set Up ◽  
Foil Thrust Bearing ◽  
Excellent Stability

Foil thrust bearings have attracted considerable attention in small-sized turbo machines with its excellent stability, high compliance, temperature durability. Geometric structure play an important role on the performance of foil thrust bearings. However, the current research on the structure mainly focuses on the underlying foil type, such as bump foil, protuberant bump. In fact, the foil profile, especially in the convergent region has significant influence. In this paper, foil thrust bearings were classified into convex, slope and concave types according to the profile curvature. A numerical model of six pads foil thrust bearing was established by combining the shell model and Reynolds equation. The static and dynamic performance of thrust bearings with different curvature was calculated. The results showed that the convex convergent possessed higher capacity and was not sensitive to displacement disturbance. A stiffness testing system for thrust foil bearing was set up, and the results verified that the foil with convex wedge had higher stiffness. The experiment also indicated that all the thrust foil bearings had typical damping hysteresis. The axial force of a 10 kW on-board compressor was calculated. Based on the conclusion of this paper, the design scheme of curvature value β = 0.6 and gas thickness h2=15 µm was given in consideration of bearing capacity and machining robustness.

Analysis of Thermal Damage in the High-Speed Foil Bearing

2017 ◽  
Vol 260 ◽  
pp. 266-277 ◽  
Author(s):  
Grzegorz Żywica ◽  
Paweł Bagiński ◽  
Artur Andrearczyk
Keyword(s):  
High Speed ◽  
Thermal Analyses ◽  
Experimental Tests ◽  
Significant Rise ◽  
Operating Conditions ◽  
Factors Affecting ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Wide Range ◽  
Heavy Loads

The article discusses experimental research and simulation testing on prototypical foil bearings. All experimental tests were conducted on a special test rig which makes it possible to operate in various conditions and within a wide range of speeds. As a result of the study, it turned out that adverse operating conditions caused almost instant bearing damage, accompanied by a significant rise in temperature. The main factors affecting the durability of foil bearings were material covering mating surfaces, bearing geometry, way of assembling the bearing, rotational speed and load. To better understand the physical phenomena occurring in foil bearings, a numerical model has been developed which allowed carrying out thermal analyses. The analysis of heat flow in the bearing's structure showed that, because of the system geometry, significant problems with proper removal of large amounts of heat continued to be experienced, which may have led to an accelerated rate of fatigue damage and shorter bearing life. This phenomenon can occur in bearings operating under tough conditions (e.g. at low speeds or under heavy loads). The research showed that the development of a new foil bearing is a very difficult task and requires many aspects to be taken into account, including the aspects directly related to the operation of the bearing itself, as well as those related to the rotor's operation and characteristics of the machine.

scholarly journals Berkovich indentation of diamondlike carbon coatings on silicon substrates

2008 ◽  
Vol 23 (7) ◽  
pp. 1862-1869 ◽  
Author(s):  
Ayesha J. Haq ◽  
P.R. Munroe ◽  
M. Hoffman ◽  
P.J. Martin ◽  
A. Bendavid
Keyword(s):  
Plastic Deformation ◽  
Cross Sections ◽  
Silicon Substrate ◽  
Chemical Vapor ◽  
Silicon Substrates ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Dlc Coating ◽  
Vapor Deposition Technique ◽  
Diamondlike Carbon

The deformation behavior of diamondlike carbon (DLC) coatings on silicon substrates induced by Berkovich indentation has been investigated. DLC coatings deposited by a plasma-assisted chemical vapor deposition technique were subjected to nanoindentation with a Berkovich indenter over a range of maximum loads from 100 to 300 mN. Distinct pop-ins were observed for loads greater than 150 mN. However, no pop-out was observed for the loads studied. The top surface of the indents showed annular cracks with associated fragmented material. The cross sections showed up to 20% localized reduction in thickness of the DLC coating beneath the indenter tip. Cracking, {111} slip, stacking faults, and localized phase transformations were observed in the silicon substrate. The discontinuities in the load–displacement curves at low loads are attributed to plastic deformation of the silicon substrate, whereas at higher loads they are attributed to plastic deformation as well as phase transformation.

Observation of Atom Rows in Thorium Pyromellitate Using a Field Emission STEM

1977 ◽  
Vol 35 ◽  
pp. 80-81
Author(s):  
H. Todokoro ◽  
S. Nomura ◽  
T. Komoda
Keyword(s):  
Field Emission ◽  
Amorphous Carbon ◽  
Carbon Film ◽  
Dark Field Image ◽  
Dark Field ◽  
Amorphous Carbon Film ◽  
Atomic Size ◽  
Wide Range ◽  
A Chain

It is interesting to observe polymers at atomic size resolution. Some works have been reported for thorium pyromellitate by using a STEM (1), or a CTEM (2,3). The results showed that this polymer forms a chain in which thorium atoms are arranged. However, the distance between adjacent thorium atoms varies over a wide range (0.4-1.3nm) according to the different authors.The present authors have also observed thorium pyromellitate specimens by means of a field emission STEM, described in reference 4. The specimen was prepared by placing a drop of thorium pyromellitate in 10-3 CH3OH solution onto an amorphous carbon film about 2nm thick. The dark field image is shown in Fig. 1A. Thorium atoms are clearly observed as regular atom rows having a spacing of 0.85nm. This lattice gradually deteriorated by successive observations. The image changed to granular structures, as shown in Fig. 1B, which was taken after four scanning frames.

scholarly journals Surface Reformation of Medical Devices with DLC Coating

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 376
Author(s):  
Mao Kaneko ◽  
Masanori Hiratsuka ◽  
Ali Alanazi ◽  
Hideki Nakamori ◽  
Kazushige Namiki ◽  
...  
Keyword(s):  
High Pressure ◽  
Medical Devices ◽  
Diamond Like Carbon ◽  
Steam Sterilization ◽  
Dlc Coatings ◽  
Chrome Plating ◽  
Living Body ◽  
Dlc Coating ◽  
Pressure Steam ◽  
Adhesion Friction

We evaluated the adhesion, friction characteristics, durability against bodily acids, sterilization, cleaning, and anti-reflection performance of diamond-like carbon (DLC) coatings formed as a surface treatment of intracorporeal medical devices. The major coefficients of friction during intubation in a living body in all environments were lower with DLC coatings than with black chrome plating. DLC demonstrated an adhesion of approximately 24 N, which is eight times stronger than that of black chrome plating. DLC-coated samples also showed significant stability without being damaged during acid immersion and high-pressure steam sterilization, as suggested by the results of durability tests. In addition, the coatings remained unpeeled in a usage environment, and there was no change in the anti-reflection performance of the DLC coatings. In summary, DLC coatings are useful for improving intracorporeal device surfaces and extending the lives of medical devices.

Foil Gas Bearing With Compression Springs: Analyses and Experiments

2007 ◽  
Vol 129 (3) ◽  
pp. 628-639 ◽  
Author(s):  
Ju-ho Song ◽  
Daejong Kim
Keyword(s):  
Loss Factor ◽  
Load Capacity ◽  
Underlying Structure ◽  
Equivalent Viscous Damping ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Different Types ◽  
Structural Loss ◽  
Compression Springs ◽  
Gas Bearing

A new foil gas bearing with spring bumps was constructed, analyzed, and tested. The new foil gas bearing uses a series of compression springs as compliant underlying structures instead of corrugated bump foils. Experiments on the stiffness of the spring bumps show an excellent agreement with an analytical model developed for the spring bumps. Load capacity, structural stiffness, and equivalent viscous damping (and structural loss factor) were measured to demonstrate the feasibility of the new foil bearing. Orbit and coast-down simulations using the calculated stiffness and measured structural loss factor indicate that the damping of underlying structure can suppress the maximum peak at the critical speed very effectively but not the onset of hydrodynamic rotor-bearing instability. However, the damping plays an important role in suppressing the subsynchronous vibrations under limit cycles. The observation is believed to be true with any air foil bearings with different types of elastic foundations.

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