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.

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.

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.

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.

scholarly journals Correlation of nanoindentation-induced deformation microstructures in diamondlike carbon coatings on silicon substrates with simulation studies

2010 ◽  
Vol 25 (5) ◽  
pp. 910-920 ◽  
Author(s):  
Ayesha J. Haq ◽  
Paul R. Munroe ◽  
Mark Hoffman ◽  
Phil J. Martin ◽  
Avi Bendavid
Keyword(s):  
Shear Stress ◽  
Silicon Substrate ◽  
Hydrostatic Stress ◽  
Dislocation Motion ◽  
Indentation Load ◽  
Cross Sectional ◽  
Carbon Coatings ◽  
Si Substrates ◽  
Transmission Electron ◽  
Diamondlike Carbon

The effect of the presence of diamondlike carbon coatings deposited on (100) Si substrates on the deformation mechanisms operating in the silicon substrate during contact loading have been investigated by both cross-sectional transmission electron microscopy and modeling of the stresses generated beneath the indenter tip. The observed subsurface microstructures were correlated to the Tresca shear stress and the hydrostatic stress generated in the silicon substrate beneath the indenter tip. The presence of the coating altered the stresses generated in the substrate, and changed the deformation mechanism from one of principally phase transformation in uncoated Si to predominantly dislocation motion in the silicon substrate for the diamondlike C–Si system. The magnitude and distribution of the shear and hydrostatic stresses in the substrate were found to depend on both the indentation load and the thickness of the coating. Furthermore, the observed width of deformation, parallel to the interface, which was found to increase with coating thickness, was correlated to the wider distribution of the Tresca shear stress in the substrate brought about by the presence of the coating.

Determination of fracture toughness from the extra penetration produced by indentation-induced pop-in

2003 ◽  
Vol 18 (6) ◽  
pp. 1412-1419 ◽  
Author(s):  
J. S. Field ◽  
M. V. Swain ◽  
R. D. Dukino
Keyword(s):  
Fracture Toughness ◽  
Crack Length ◽  
Radial Crack ◽  
Brittle Materials ◽  
Critical Stress Intensity Factor ◽  
Fused Silica ◽  
Modulus Ratio ◽  
Material Volume ◽  
Radial Cracks

The fracture toughness of small volumes of brittle materials may be investigated by using pyramidal indenters to initiate radial cracks. The length of these cracks, together with indenting load and the hardness to modulus ratio of the material, were combined to calculate the critical stress intensity factor Kc pertinent to fracture toughness. Modulus and hardness may be obtained from the literature or may be measured using nanoindentation techniques. If the material volume is very small, such as single grains in a conglomerate, a reduction of scale may be obtained by reducing the internal face angles of the indenter. This encourages crack initiation at lower loads, but cracks produced at very low loads are short and difficult to measure. Experiments on fused silica and glassy carbon suggested that radial cracks are initiated during loading and that when indenters with sufficiently small angles are used these cracks immediately pop-in, to become fully developed median/radial crack systems. Following pop-in, the rate of penetration of the indenter increases and at higher loads there is an extra increment of penetration over that which would otherwise have occurred. In this study a method is described whereby this extra penetration may be determined. Then for two dissimilar brittle materials, crack length is shown to be correlated with extra penetration leading to a relationship that may possibly avoid the necessity for crack-length measurement.

Sliding Wear of Non-Hydrogenated Diamond-Like Carbon Coatings Against Al, Cu and Ti

2005 ◽  
Author(s):  
E. Konca ◽  
Y. T. Cheng ◽  
A. T. Alpas
Keyword(s):  
Sliding Wear ◽  
Ambient Air ◽  
Inert Atmosphere ◽  
Diamond Like Carbon ◽  
Severe Damage ◽  
Material Transfer ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Dlc Coating ◽  
Pin On Disc

Magnetron sputtered non-hydrogenated diamond-like carbon (DLC) coatings were tested against Al, Cu and Ti pins using a vacuum pin-on-disc tribometer. The objective was to compare Al, Ti, and Cu transfer to DLC coatings in air (29% RH) and an inert atmosphere (argon). In argon, a significant amount of adhesion and material transfer occurred from the Al and Ti pins to the DLC coating surfaces inflicting severe damage to the coatings. Wear and material transfer of the DLC coating against Cu were negligible in argon. Compared to tests in argon, the tribological performance of the DLC coatings against Al and Ti improved significantly in ambient air. In contrast, the wear rate of the DLC coatings against Cu was much higher in ambient air compared to that in argon.

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.

Prediction of Fracture Toughness in Fibrous Si3 N4 Monolithic Ceramics

2006 ◽  
Vol 317-318 ◽  
pp. 301-304
Author(s):  
Hai Guo ◽  
Dae Hyun Yoon ◽  
Dong Woo Shin
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Crack Propagation ◽  
Mirror Image ◽  
Propagation Path ◽  
Displacement Curve ◽  
Total Work ◽  
Crack Propagation Path ◽  
Monolithic Ceramics ◽  
Work Of Fracture

A fracture toughness model of fibrous monolithic ceramics revealed that the major factor that contributed to the fracture toughness in ceramics was the actual energy absorbed by crack propagation rather than the total work of fracture. The load-displacement curve and the crack propagation path were predicted using the derived model mirror image with that of experimental data.

Effects of Interlayer on Mechanical Properties of Diamond-Like Carbon Coatings

2018 ◽  
Vol 883 ◽  
pp. 43-47 ◽  
Author(s):  
Sun Hui Yao ◽  
Yan Liang Su ◽  
Yu Chen Lai ◽  
Huang Ming Wu
Keyword(s):  
Mechanical Properties ◽  
Diamond Like Carbon ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Mechanical And Tribological Properties ◽  
Dlc Coating ◽  
Unbalanced Magnetron Sputtering ◽  
Unbalanced Magnetron ◽  
The One ◽  
Sputtering System

This paper reports comparative studies on effects of interlayer on mechanical properties of diamond-like carbon (DLC) coatings. Two interlayers, TiC/Ti and CrC/Cr, were deposited and studied. The DLC coatings were prepared by using an unbalanced magnetron sputtering system. The chemical composition, micro-structure, constituted phases, and fundamental mechanical and tribological properties were evaluated. The results showed that the two amorphous (a-) DLC coatings were obtained. The a-DLC coating with the TiC/Ti interlayer showed higher adhesion, hardness and wear resistance than the one with the CrC/Cr interlayer.

Morphology of Fibroblastic Cells Cultured on Diamond-Like Carbon Coatings Produced by Plasma Immersion Using AFM and SEM

2006 ◽  
Vol 309-311 ◽  
pp. 713-716 ◽  
Author(s):  
E.T. Uzumaki ◽  
C.S. Lambert ◽  
L.O. Bonugli ◽  
A.R. Santos ◽  
Cecília A.C. Zavaglia
Keyword(s):  
Biological Effects ◽  
Diamond Like Carbon ◽  
Electron Microscopic ◽  
Adhesion Properties ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Dlc Coating ◽  
Atomic Force ◽  
Fibroblastic Cells ◽  
Potential Use

For the potential use of diamond-like carbon (DLC) coating for biomedical applications, it would be important to evaluate the biological effects of these coatings. In this study, DLC coatings were deposited on glass coverslips using the plasma immersion process, which produces films with adhesion properties superior to those prepared with conventional techniques. Scanning electron microscopic and atomic force microscopic observations were used to study the morphology of fibroblasts growth on DLC coatings.

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