NASA/TMm2000-209088 / PART 3

Friction and Wear Properties of Selected

Solid Lubricating Films

Part 3: Magnetron-Sputtered and Plasma-Assisted,

Chemical-Vapor-Deposited Diamondlike Carbon Films

Kazuhisa Miyoshi

Glenn Research Center, Cleveland, Ohio

Masanori Iwaki, Kenichi Gotoh, Shingo Obara, and Kichiro Imagawa

Tsukuba Space Center, Tsukuba, Ibaraki, Japan

%,-

4

June 2000

https://ntrs.nasa.gov/search.jsp?R=20000082019 2018-05-15T14:18:57+00:00Z
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NASA/TMD2000-209088/PART 3

Friction and Wear Properties of Selected

Solid Lubricating Films

Part 3: Magnetron-Sputtered and Plasma-Assisted,

Chemical-Vapor-Deposited Diamondlike Carbon Films

Kazuhisa Miyoshi

Glenn Research Center, Cleveland, Ohio

Masanori Iwaki, Kenichi Gotoh, Shingo Obara, and Kichiro Imagawa

Tsukuba Space Center, Tsukuba, Ibaraki, Japan

National Aeronautics and

Space Administration

Glenn Research Center

June 2000
Acknowledgment

This research activity was basic research conducted under the Reimbursable Space Act Agreement

between N-ASA Glenn Research-Center _,hdK Systems Corp0rafi-on for Measurements and

Analysis of Aerospace Tribology for Various Materials.

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

Price Code: A03

Available from

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22100

Price Code: A03
FRICTION AND WEAR PROPERTIES OF SELECTED SOLID

LUBRICATING FILMS

Part 3: Magnetron-Sputtered and Plasma-Assisted, Chemical-Vapor-Deposited

Diamondlike Carbon Films

Kazuhisa Miyoshi

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44 i 35

Masanori Iwaki, Kenichi Gotoh, Shingo Obara, and Kichiro Imagawa

National Space Development Agency of Japan

Tsukuba Space Center

Tsukuba, Ibaraki 305-8505 Japan

SUMMARY

To evaluate commercially developed dry solid film lubricants for aerospace bearing applications, an investigation was conducted to examine the friction and wear behavior of magnetron-sputtered diamondlike carbon (MS

DLC) and plasma-assisted, chemical-vapor-deposited diamondlike carbon (PACVD DLC) films in sliding contact

with 6-mm-diameter American Iron and Steel Institute (AISI) 440C stainless steel balls. Unidirectional sliding friction experiments were conducted with a load of 5.9 N (600 g), a mean Hertzian contact pressure of 0.79 GPa (maximum Hertzian contact pressure of 1.2 GPa), and a sliding velocity of 0.2 m/s. The experiments were conducted at

room temperature in three environments: ultrahigh vacuum (vacuum pressure, 7x10 -7 Pa), humid air (relative

humidity, ~20 percent), and dr3' nitrogen (relative humidity, <1 percent). The resultant films were characterized by

scanning electron microscopy, energy-dispersive x-ray spectroscopy, and surface profilometry.

Marked differences in the friction and wear of the DLC films investigated herein resulted from the environmental conditions. The main criteria for judging the performance of the DLC films were coefficient of friction and

wear rate, which had to be less than 0.3 and on the order of 10--6 mm3/N.m or less, respectively. MS DLC films and

PACVD DLC films met the criteria in humid air and dry nitrogen but failed in ultrahigh vacuum, where the coefficients of friction were greater than the criterion, 0.3. In sliding contact with 440C stainless steel balls in all three

environments the PACVD DLC films exhibited better tribological performance (i.e., lower friction and wear) than

the MS DLC films. All sliding involved adhesive transfer of wear materials: transfer of DLC wear debris to the

counterpart 440C stainless steel and transfer of 440C stainless steel wear debris to the counterpart DLC film.

INTRODUCTION

Diamondlike carbon (DLC) can be divided into two closely related categories known as amorphous,

nonhydrogenated DLC (a-DLC or a-C) and amorphous, hydrogenated DLC (H-DLC or a-C:H) (ref. 1). H-DLC

contains a variable and appreciable amount of hydrogen. DLCcan be considered as a metastable carbon produced as

a thin film with a broad range of structures (primarily amorphous with variable sp2/sp 3 bonding ratio) and compositions (variable hydrogen concentration). A DLC's properties can vary considerably as its structure and composition

vary (refs. 2 to 5). Although it is a complex engineering job, it is often possible to control and tailor the properties

of a DLC to fit a specific application and thus ensure its success as a tribological product. However, such control

demands a fundamental understanding of the tribological properties of DLC films. The absence of this understanding can act as a brake in applying DLC to a new product and in developing the product.

Tribological applications of DLC coatings and films are already well established in a number of fast-growing

markets, such as magnetic recording media, high-density magnetic recording disks and sliders (heads), process

equipment (e.g., copy machines and digital video camcorders), abrasion-resistant optical products, medical devices,

implant components (including hip joints and knee implants), packaging materials, electronic devices, plastic molds,

gear pumps, stamping devices, forming dies, blades (e.g., razor blades and scalpel knives), engine parts (e.g.,

NAS A/TM--2000-209088/PART 3 1
gudgeonpins),washers(e.g.,grease-free ceramicfaucetvalveseats),seals,valves,gears,bearings, bushings, tools,

andwearparts(refs.6to9).ThecostisgenerallysimilartothatofcarbideornitridefilmsdepositedbyCVDor

physical vapordeposition(PVD)techniques. Thesurfacesmoothness, highhardness, lowcoefficient of friction,

lowwearate,andchemical inertnessofDLCcoatingsandfilms,alongwithlittlerestrictionofgeometryandsize,

makethemwellsuitedassolidlubricantsforapplicationsinvolvingwearandfriction.

Inparts1and2oftheinvestigation(refs.t0 and1I),fourtypesofselectedsolidlubricatingfilmwereexaminedinultrahighvacuum, inhumidairatarelativehumidityofapproximately 20percent, andindrynitrogen

atarelativehumidityoflessthan1percent.Thefourtypeswerebondedmolybdenumdisulfide(MoS2)films,

magnetron-sputtered MoS2films,ion-platedsilverfilms,andion-platedleadfilms.

Thepresent investigation(part3)wasconductedtoexaminethefrictionandwearpropertiesofmagnetronsputtereddiamondlikecarbon(MSDLC)andplasma-assisted, chemical-vapor-deposited diamondlikecarbon

(PACVDDLC)filmsinthesamemannerasinthepartsI and2investigations. BothMSDLCandPACVDDLC

filmscanbeconsideredasa-DLC(amorphous, nonhydrogenated DLC).Magnetronsputteringandplasma-assisted

CVDpermitclosecontroloffilmdepositionandthickness, canprovidegoodadhesiontothesubstrate, andcan

producemultilayercoatings. Unidirectional pin-on-diskslidingfrictionexperiments wereconductedwith"440C

stainless steel balls in sliding contact with the solid lubricating films at room temperature in ultrahigh vacuum

(7x10 -7 PaL in humid air (relative humidity, -20 percent), and in dry nitrogen (relative humidity, <1 percent). The

resultant solid lubricating films and their wear surfaces were characterized by scanning electron microscopy (SEM),

energy-dispersive x-ray spectroscopy (EDX), and surface profilometry. SEM and EDX were used to determine the

morphology and elemental composition of wear surfaces, wear debris, and wear of the balls. The sampling depth of

EDX for elemental information ranged between 0.5 and 1 ram in this investigation. Surface profilometry was used to

determine the surface morphology, roughness, and wear of the coatings.

SELECTED MATERIALS

Three specimens of each film type, MS DLC and PACVD DLC, produced on 440C stainless steel disk substrates were used in this investigation (table I). The MS DLC films had a multilayer structure and were prepared

using two chromium targets, 6 tungsten carbide (_7C) targets, and methane (CH 4) gas. Each multilayer film comprised WC layers (20 to 50 nm thick) alternating with carbon layers (20 to 50 nm thick). The Vickers hardness number was approximately 1000. The 2- to 3-1_m-thick MS DLC films were relatively smooth, and their

centerline-average roughness Ra, measured using a cutoff of 1 mm, was 43 nm with a standard deviation of 5.1 nm.

The PACVD DLC films were prepared using radiofrequency plasma and consisted of two layers. Each film

comprised an approximately 2-_m-thick DLC layer on an approximately 2-_tm-thick silicon-DLC underlayer. The

top DLC layer was deposited using CH 4 gas at a total pressure of 8 Pa with a power of t 800 to 2000 W at -750 to

-850 V for t 20 rain. The silicon-containing DLC underlayer was deposited using a mixture of CH 4 and C4HI2Si

(tetramethylsilane) gases. The ratio of the concentrations of CH 4 and C4HI2Si used was 90:18 (std cm3/min) at a

total pressure of 10 Pa with a power of 1800 to 2000 W at -850 to -880 V for 60 min. The Vickers hardness number

was 1600 to 1800. The 3- to 5-1am-thick PACVD DLC films were also relatively smooth and their R a, measured

using a cutoff of 1 mm, was 29 nm with a standard deviation of 3.2 nm. The 6-mm-diameter 440C stainless steel

balls (grade number, 10) used were smooth having an Ra of 0.025 larn with a standard deviation of 0.02 lain or less.

EXPERIMENT

The pin-on-disk tribometer used in the investigation was mounted in a vacuum chamber (refs. 10 and 11).

Unidirectional pin-on-disk sliding friction experiments were conducted at room temperature in ultrahigh vacuum

(7x10 -7 Pa), in humid air (relative humidity, -20 percent), and in dry nitrogen (relative humidity, <1 percent). All

experiments were conducted with 6-mm-diameter 440C stainless steel balls in sliding contact with the DLC films

deposited on 440C stainless steel substrate disks. All experiments were conducted with a load of 5.9 N (600 g) at

the sliding velocity of 0.2 m/s. The mean Hertzian contact pressure of the 440C stainless steel substrates in contact

with the 440C stainless steel balls was approximately 0.79 GPa (maximum Hertzian contact pressure, 1.2 GPa). The

pin-on-disk tribometer can measure friction in vacuum, in humid air, and in dry nitrogen during sliding. The friction

force was continuously monitored during the sliding friction experiments.

NAS A/TM----2000-209088/PART 3 2
Theslidingwearlife(filmwearlifeorfilmendurancelife)forthecoatingsinthisinvestigationwasdetermined

tobethenumberofpassesatwhichthecoefficient offrictionroseto0.3inagivenenvironment. Wearwasquantifiedbymeasuringthewearscarsandweartracksonthespecimensafterthewearexperiments. Filmwearvolumes

wereobtainedbyaveragingthecross-sectional areas,determinedfromstylustracings, measuredacrossthewear

tracksataminimumoffourlocationsineachweartrack.Then,theaveragecross-sectional areaoftheweartrack

wasmultipliedbytheweartracklength.Thewearate,knownasthedimensional wearcoefficient, isdefinedasthe

volumeofmaterialremovedataunitloadandinaunitslidingdistanceexpressedascubicmillimetersper

newton .meter.

RESULTS AND DISCUSSION

Friction Behavior

Figures 1 to 3 present typical friction traces obtained in ultrahigh vacuum, in humid air, and in dry nitrogen,

respectively, for the MS DLC and PACVD DLC films in sliding contact with 440C stainless steel balls as a function

of the number of passes. All the friction traces for the DLC films obtained in the three environments fluctuated. In

ultrahigh vacuum (fig. 1) the coefficient of friction for both the MS DLC and PACVD DLC films rose to 0.3 in a

few passes; the steady-state values were approximately 0.7 for the MS DLC films and 0.54 for the PACVD DLC

films. In humid air (fig. 2) the coefficients of friction for both the MS DLC and PACVD DLC films decreased

to approximately 0.1 ; the steady-state value for the PACVD DLC films was generally lower than that for the MS

DLC films. In dry nitrogen (fig. 3) the coefficient of friction for the MS DLC films increased to 0.3 at approximately

24 000 passes, and the steady-state coefficient of friction for the PACVD DLC films decreased to 0.05 at 300 000

passes.

Comparing the data taken in the different environments (figs. 1 to 3) shows that the coefficients of friction for

both the MS DLC and PACVD DLC films were much higher in ultrahigh vacuum than in humid air and in dry nitrogen. The coefficients of friction of the PACVD DLC films were generally lower than those of the MS DLC films in

all three environments.

Wear Behavior

Figures 4 to 6 present SEM photomicrographs of wear tracks on the MS DLC and PACVD DLC films deposited on 440C stainless steel disks and the wear scars on the 440C stainless steel balls in ultrahigh vacuum, in hunfid

air, and in dry nitrogen, respectively. The SEM observations were made at I000 passes in ultrahigh vacuum, at

300 000 passes in humid air, and either at the end of film wear life or at 300 000 passes in dry nitrogen. In ultrahigh

vacuum (fig. 4) the sliding action roughened the entire wear tracks of the MS DLC films at 1000 passes but locally

produced micro-pits in the wear tracks of the PACVD DLC films. With both films types in ultrahigh vacuum, wear

debris particles and agglomerated wear debris were generated during sliding. In humid air the sliding action generated smooth wear surfaces on the MS DLC films and deposited a large amount of agglomerated, pasty wear debris

on the wear scars of the 440C stainless steel balls (fig. 5(a)). In humid air the sliding action generated a smooth wear

surface on the PACVD DLC films with relatively large wear debris particles (fig. 5(b)). In dry nitrogen the sliding

action generated a smooth wear surface for both film types and produced fine wear debris particles with the MS

DLC films (fig. 6(a)) and relatively large wear debris particles with the PACVD DLC films (fig. 6(b)).

The wear scars on the 440C stainless steel balls were generally smooth, regardless of the environment. Thin,

smeared wear patches and particles of the DLC films generally covered the smooth wear scars. Smeared tongues of

thin, layered, agglomerated wear debris were also present. Most of the loose and smeared wear debris accumulated

outside the wear scars.

Wear (Endurance) Life

As in parts 1 and 2 of the investigation (refs. 10 and i I) the sliding wear (endurance) life of the solid lubricating

films deposited on 440C stainless steel disks was determined to be the number of passes at which the coefficient of

NAS A/TM--2000-209088/PART 3 3
frictionroseto0.3.Theslidingwearlivesof theDLCfilmsexaminedinthisinvestigation(tableII) variedwiththe

environment. Whenjudgedbythecoefficientoffriction,thewearlivesofbothfilmtypeswereextremelyshortin

ultrahighvacuum.TheMSDLCfilmshadmuchlongerwearlivesinhumidairthanindr),nitrogenandinultrahigh

vacuum.ThePACVDDLCfilmshadmuchlongerwearlivesinhumidairandindrynitrogenthaninultrahigh

vacuum,

ComparisonofSteady-State CoefficientsofFrictionandWearRates

TableII alsopresentshesteady-statecoefficientsoffrictionandthefilmandballwearatesafterslidingcontactinallthreeenvironments. Thedatapresentedinthetablerevealthemarkedifferencesincoefficientoffriction

resultingfromtheenvironmental conditions. BoththeMSDLCandPACVDDLCfilmshadhighcoefficientsof

friction,highfilmwearates,andhighballwearatesinultrahighvacuumbutrelativelylowcoefficientsoffriction,

lowfilmwearates,andlowballwearratesinhumidairandindrynitrogen. Bothfilmtypesmetthemaincriteria

forjudgingthetribological performanceoffilms(coefficient offrictionlessthan0.3andwearateontheorder

of 10-6mm3/N.morless)inhumidairandindrynitrogen.Inslidingcontactwitha440Cstainlesssteelballthe

PACVDDLCfilmsexhibitedbettertribological performance(i.e.,lowerfrictionandwear)thandidtheMSDLC

filmsinallthreeenvironments.

SlidingWear,WearDebris,andTransferredWearFragments

ExaminingthemorphologyandcompositionofthewornsurfacesofMSDLCandPACVDDLCfilmsin

slidingcontactwith440CstainlesssteelballsbySEMandEDXprovidedetailedinformationaboutplasticdeformationoftheDLCfilms,weardebris,andtransferredwearfragmentsproducedduringsliding(figs.7to12).All

slidinginvolvedgenerationoffineweardebrisparticlesandagglomerated weardebrisandtransferoftheworn

materials.

Ultra-high-vacuum environment. Figure 7(a) presents a typical wear track on an MS DLC film over which

a 440C stainless steel ball has passed in ultrahigh vacuum leaving a roughened worn DLC film surface and a small

amount of transferred steel wear fragments. The wear scar on the counterpart 440C stainless steel ball (fig. 7(b))

contained fine steel wear debris particles and a small amount of transferred DLC wear fragments. The wear mechanism for an MS DLC film in sliding contact with a 440C stainless steel ball in ultrahigh vacuum is that of small

DLC fragments chipping off the surface.

Figure 8(a) presents a typical wear track on a PACVD DLC film over which a 440C stainless steel ball has

passed in ultrahigh vacuum leaving smeared, agglomerated DLC wear debris and a small amount of transferred

steel wear fragments. The wear scar on the counterpart 440C stainless steel ball (fig. 8(b)) contained fine steel wear

debris particles and large smeared, agglomerated wear debris patches containing transferred DLC wear fragments.

The wear mechanism for a PACVD DLC film in sliding contact with a 440C stainless steel ball in ultrahigh vacuum

was adhesion, and plastic deformation played a role in the burnished appearance of the agglomerated wear debris.

Humid-air environment. Figure 9(a) presents a typical wear track on an MS DLC film over which a 440C

stainless steel ball has passed in humid air leaving a small amount of transferred steel wear fragments. The fine

asperities of the MS DLC film were flattened and elongated in the sliding direction by plastic deformation, revealing

a smooth, burnished appearance. The entire wear scar on the counterpart 440C stainless steel ball (fig. 9(b)) contained thick transferred layers (or sheets) of MS DLC. Plate-like DLC wear debris particles were found at the edges

of the wear scar. Severe plastic deformation and sheafing occurred in the DLC film during sliding.

Figure 10(a) presents a typical wear track on a PACVD DLC film over which a 440C stainless steel ball has

passed in humid air leaving a small amount of transferred steel wear fragments. The fine asperities of the PACVD

DLC film were flattened and elongated in the sliding direction by plastic deformation, revealing a smooth, burnished

appearance. The smooth wear scar on the counterpart 440C stainless steel ball (fig. 10(b)) contained an extremely

small amount of transferred PACVD DLC wear debris.

Dry-nitrogen environment.--Figure 11(a) presents a typical wear track on an MS DLC film over which a 440C

stainless steel ball has passed in dr), nitrogen. At 23 965 passes (end of life) there was an extremely small amount of

transferred steel wear debris, and the fine asperities of the MS DLC film were flattened and elongated in the sliding

direction by plastic deformation, revealing a smooth, burnished appearance. In addition to the small amount of steel

NAS A/TM--2000-209088/PART 3 4
weardebrisparticles,meared, agglomerated DLCweardebriswasfoundontheMSDLCfilm.Plasticdeformation

occurredintheDLCfilmduringsliding.Thewearscaronthecounterpart 440Cstainlesssteelball(fig.11(b))containedtransferredDLCweardebrisparticlesandpatches.

Figure12(a)presentsatypicalweartrackonaPACVDDLCfilmoverwhicha440Cstainlesssteelballhas

passedindrynitrogen.At300000passesDLCweardebris,micro-pits, andanextremelysmallamountoftransferredsteelweardebriswereobserved. Thewearscaronthecounterpart 440Cstainlesssteelball(fig.12(b))containedfinegroovesintheslidingdirection, steelweardebris,andtransferredDLCweardebris.

CONCLUSIONS

Toevaluaterecentlydevelopeddiamondlikecarbon(DLC)filmlubricantsforaerospacebaringapplications,

unidirectional slidingfrictionexperimentswereconductedwithDLCfilmsinslidingcontactwithAIS1440C

stainlesssteelballsinultrahighvacuum, inhumidair,andindrynitrogen. ThemaincriteriaforjudgingtheperformanceoftheDLCfilmswerecoefficientoffrictionandwearate,whichhadtobelessthan0.3andontheorderof

10_5mm3/N.morless,respectively. Thefollowingconclusionsweredrawn:

1.Magnetron-sputtered (MS)DLCfilmsandplasma-assisted, chemical-vapor-deposited (PACVD)DLCfilmsmet

thecriteriainhumidairandindrynitrogenbutfailedinultrahighvacuum,wherethecoefficientsoffriction

weregreaterthanthecriterion,0.3.

2. Inslidingcontactwitha440CstainlesssteelballthePACVDDLCfilmsexhibitedbettertriboiogical performance(i.e.,lowerfrictionandwear)inallthreeenvironments thantheMSDLCfilms.

3.All slidinginvolvedadhesivetransferofwearmaterials: transferofDLCweardebristothecounterpart 440C

stainlesssteelballandtransferof440Cstainlesssteelweardebristothecounterpart DLCfilm.

REFERENCES

1.Pierson,H.O.:HandbookofCarbon,Graphite, Diamond, andFullerenes: Properties, Processing, andApplications.NoyesPublications, ParkRidge,NJ,1993.

2.Pouch,J.J.;andAlterovitz,S.A.,eds.:PropertiesandCharacterization ofAmorphousCarbonFilms.Materials

ScienceForum,Vols.52and53,TransTechPublications, Switzerland, 1990.

3. Miyoshi,K.;Pouch,J.J.; and Alterovitz, S.A.: Plasma-Deposited Amorphous Hydrogenated Carbon Films and

Their TribologicaI Properties. Properties and Characterization of Amorphous Carbon Films, J.J. Pouch and

S.A. Alterovitz, eds., Materials Science Forum, Vols. 52 and 53, Trans Tech Publications, Switzerland, 1990,

pp. 645-656.

4. Wu, R.L.C.; Miyoshi, K.; Vuppuladhadium, R.; and Jackson, H.E.: Physical and Tribological Properties of

Rapid Thermal Annealed Diamond-like Carbon Films. Surface and Coatings Technology, vol. 55, 1992,

pp. 576-580.

5. Miyoshi, K.; et al.: Sliding Wear and Fretting Wear of Diamondlike Carbon-Based, Functionally Graded

Nanocomposite Coatings. Wear, vol. 229, 1999, pp. 65-73.

6. Molloy, A.P.; and Dionne, A.M., eds., World Markets, New Applications, and Technology for Wear and

Superhard Coatings. Gorham Advanced Materials, Inc., Gorham, ME, 1998.

7. Miyoshi, K.: Lubrication by Diamond and Diamondlike Carbon Coatings. J. Tribology, vol. 120, no. 2, 1998,

pp. 379-384.

8. Miyoshi, K.; et al.: CVD Diamond, DLC, and c-BN Coating for Solid Film Lubrication. Tribology Letters,

vol. 5, 1998, pp. 123-129.

9. Miyoshi, K.: Tribological Characteristics and Applications of Superhard Coatings: CVD Diamond, DLC, and

c-BN. Proceedings of Applied Diamond Conference/Frontier Carbon Technology Joint Conference 1999,

Tsukuba, Japan (adc99@icube-t.co.jp). (Also NASA TM--1999-209189.)

10. Miyoshi, K.; et al.: Friction and Wear Properties of Selected Solid Lubricating Films, Part I: Bonded and

Magnetron-Sputtered Molybdenum Disulfide and Ion-Plated Siver Films. NASA/TM--1999-209088/

PART 1, 1999.

11. Miyoshi, K.: Friction and Wear Properties of Selected Solid Lubricating Films, Part 2: Ion-Plated Lead Films.

NASA TM--2000-209088/PART 2, 2000.

NASA/TM--2000-209088/PART 3 5
TABLE I.--CHARACTERISTICS OF SELECTED SOLID

LUBRICATING FILMS

[Film material, carbon; substrate material, 440C stainless steel.]

Film type Film Surface roughness of films.

Magnetron-sputtered

diamondlike carbon (MS DLC)

i_lasma-assisted, chemicalvapor-deposited diamondlike

carbon (PACVD DLC)

thickness.

pm

2-3

3-5

Ru_

nm

Mean Standard

deviation

43 5.1

29 3.2

Magnetronsputtered DLC

TABLE II.--STEADY-STATE COEFFICIENT OF FRICTION, WEAR LIFE,

AND WEAR RATES FOR DLC FILMS IN SLIDING CONTACT WITH

440C STAINLESS TEEL BALLS

Film Environment Steady-state Film wear Film wear Ball wear

coefficient of (endurance) rate, rate,

friction life a nma 3,CN.m nm13/N.m

Vacuum 0.70 <10 5.7×10 -_ 3.2×10 -4

Plasma-assisted

CVD DLC

Air 0.12

iNitrogen 0.12

Vacuum 0.54

Air 0.07

Nitrogen 0.06

>3×10 _

23 965

<10

>3×10 _

>3×10 _

1.1xlO -_

l.OxltY _

l.lxlO -s

1.8xlO -a

2.3x10 -8

6.4x10 -9

_Film wear life is determined to be the number of passes at which the coefficient of

friction rose to 0.3.

NASA/TM--2000-209088/PART 3 6
0

0

I ......1 . I I

2 4 6 8 10x10 2

Number of passes

0,8 --

f..

O

_ 0.6

"6

0.4

_0.2

(b)

0

0

1 I 1_____ .... J

2 4 6 8 10x102

Number of passes

Figure 1.--Friction traces for (a) MS DLC film and

(b) PACVD DLC film in sliding contact with 440C

stainless steel balls in ultrahigh vacuum.

._)_ 0.4 (_a) "_ "- 0.2

0_" 0 r-r--=-`'_ ":'--..... t--_" ,.,,,;_,,_-,'-,_.,,,._._,L,,L, _..,J,,,l ,,,-,,_lv,,W,_lal!_-I ,, I

0 0.6 1.2 1.8 2.4 3.0x10 5

Number of passes

.,-.'_ 0.4

o ol

0 0.6 1.2 1.8 2.4 3.0x105

Number of passes

Figure 2.--Friction traces for (a) MS DLC film and

(b) PACVD DLC film in sliding contact with 440C

stainless steel balls in humid air.

0.8 - (a)

0.8 _ 0.6 --

0.6 0.4 --

0.4: 0.2

02 ,o,

o _ 1 I t ___1

0 0.6 1.2 1.8 2.4 3.0xl 05

Number of passes

"6 0.4 I-- (b)

"_ "- 0,2

° 0

0 0.6 1.2 _ 1.8 2.4 3.0xl 05

Number of passes

Figure 3.--Friction traces for (a) MS DLC film and

(b) PACVD DLC film in sliding contact with 440C

stainless steel balls in dry nitrogen.

NASA/TM--2000-209088/PART 3 7
Film wear track Ball wear scar

(a) Sliding direction

' 'i

100 I_m 100 I_m

(b) Sliding direction

Figure 4.mWear tracks and wear scars in ultrahigh vacuum at 1000 passes. (a) Materials pair of MS DLC film and

440C stainless steel ball. (b) Materials pair of PACVD DLC film and 440C stainless steel ball.

NAS A/TM--2000-209088/PART 3 8
Film wear track Ball wear scar

(a) Sliding direction

(b) Sliding direction

Figure 5._Wear tracks and wear scars in humid air at 300 000 passes. (a) Materials pair of MS DLC film and

440C stainless steel ball. (b) Materials pair of PACVD DLC film and 440C stainless steel ball.

NASA/TM--2000-209088/PART 3 9
(a)

Film wear track

100 _m

Sliding direction

Ball wear scar

(b) Sliding direction

Figure 6.mWear tracks and wear scars in dry nitrogen. (a) Materials pair of MS DLC film and 440C stainless

steel ball at 23 965 passes. (b) Materials pair of PACVD DLC film and 440C stainless steel ball at 300 000

passes,

NASA/TM--2000-209088/PART 3 10
SEM

(a)

1.0x105

0.5-

o

0

0

EDX

,,Sik and W m

p_

li

fl

•, ii

-'k i] ^ __ W I

- 1 -I -VI V--t -1 I

2 4 6 8 10 12 14

Energy, keV

O_

0.5

L)

1.0x10 5

-- iFek

Ck n C_kil

Si k a d

_! tA/ ! !

I vvm i l _ 1

0 2 4 6 8 10 12 14

(b) Energy, keY

Figure 7.mMorphoIogy and elemental composition by SEM and EDX (a) of wear track produced on MS DLC

film and (b) of wear scar produced on 440C stainless steel ball at 1000 passes in ultrahigh vacuum.

NASA/TM--2000-209088/PART 3 l I
SEM EDX

(a)

3.0x10 5

2.5

2,0

0

o 1.0

0.5

0

i Sik

h

- !1

_k i_ Crk--", Fek

r.... T_---r_ i . i - 1

0 2 4 6 8 10 12 14

Energy, keV

1.0x105

-- _Fek

fl

_0.5 Crk 17

o Ck '4 ii

0 Sik Jl ii

it ,,,,--Sk jl I t

o I 1 1 _--I---_---I

10 _ 0 2 4 6 8 10 12 14

(b) Energy, keV

Figure 8.--Morphology and elemental composition by SEM and EDX (a) of wear track produced on PACVD DLC

film and Co)of wear scar produced on 440C stainless steel ball at 1000 passes in ultrahigh vacuum.

NASA/TM--2000-209088/PART 3 12
SEM EDX

(a)

10 _m

1.0x105 :Sikand Wm

0.5

Ck,j; i Crk ____Fek N ik_/L ,_

0 2 4 6 8 10 12 14

Energy, keV

1.0x1__05 i Sik and Wm

0 ' Ji W

0 2 4 6 8 10 12 14

(b) Energy, keV

Figure 9.mMorphology and elemental composition by SEM and EDX (a) of wear track produced on MS DLC

film and (b) of wear scar produced on 440C stainless steel ball at 300 000 passes in humid air.

NASA/TM--2000-209088/PART 3 13
SEM EDX

2.0xl 05

II

II

1.5 li

o i!

0.5 tl

i,___.._,i i Crk --",, Fe k

0

0 2 4 6 8 10 12 14

Energy, keV

o.5

o

1.0xl 05

-- rlFek

J_

Crki i

;k r-Si k [/ ]I is. il/I

0

10 I_m 2 4 6 8 10 12 14

(b) Energy, keV

Figure 10.--Morphology and elemental composition by SEM and EDX (a) of wear track produced on PACVD

DLC film and (b) of wear scar produced on 440C stainless steel ball at 300 000 passes in humid air.

NASA/TM--2000-209088/PART 3 14
SEM EDX

(a)

1.0xl 0 5

g o.5

o

0

0

l,Sik and W m

_i

Ck i!i _ Ark

, ^ . Wl

0 2 4 6 8 10 12 14

Energy, keV

(b)

1.0xl 0 5

L)

0

0

_Fek

CF_!!

_-Sikand _ ii

2 4 6 8 10 12 14

Energy, keV

Figure 11 .--Morphology and elemental composition by SEM and EDX (a) of wear track produced on MS DLC

film and (b) of wear scar produced on 440C stainless steel ball at 23 965 passes in dry nitrogen

NAS A/TM--2000-209088/PART 3 15
SEM EDX

(a)

2.5x105

ck

2.0

1.5

8 1.0

0.5

Sik

u ii Cr- --_

i!_'; ;_ K \ Fek

=;=I---F --F I l _---1

0 2 4 6 8 10 12 14

Energy, keV

1.0x105

_- !iFek

8 !, !',

I/ . : !!

_J ,'--SIk i i i,',

ot _- F-_ l_-P 1 -- I I

0 2 4 6 8 10 12 14

(b) Energy, keV

Figure 12.mMorphology and elemental composition by SEM and EDX (a) of wear track produced on PACVD

DLC film and (b) of wear scar produced on 440C stainless steel ball at 300 000 passes in dry nitrogen.

NASA/TM--2000-209088/PART 3 16

REPORT DOCUMENTATION PAGE FormApproved

OMB No. 0704-0188

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

June 2000 Technical Memorandum

4. TITLE AND SUBTITLE

Friction and Wear Properties of Selected Solid Lubricating Films

Part 3: Magnetron-Sputtered and Plasma-Assisted, Chemical-Vapor-Deposited

Diamondlike Carbon Films

6. AUTHOR(S)

Kazuhisa Miyoshi, Masanori Iwaki, Kenichi Gotoh, Shingo Obara,

and Kichiro Imagawa

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

5. FUNDING NUMBERS

WU- 297-60--0(0-_

8. PERFORMING ORGANIZATION

REPORT NUMBER

E-12214

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TMI2000-209088-

PART 3

11. SUPPLEMENTARY NOTES

Kazuhisa Miyoshi, NASA Glenn Research Center, Cleveland, Ohio; Masanori Iwaki, Kenichi Gotoh, Shingo Obara, and

Kichiro Imagawa, National Space Development Agency of Japan, Tsukuba Space Center, Tsukuba, Ibaraki 305-8505,

Japan. Responsible person, Kazuhisa Miyoshi, organization code 5160, (216) 433-6078.

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Unclassified - Unlimited

Subject Category: 27 Distribution: Nonstandard

This publication is available from the NASA Center for AeroSpace Information, (301) 621-0390.

13. ABSTRACT (Maximum 200 words)

To evaluate commercially developed dry solid film lubricants for aerospace bearing applications, an investigation was conducted to examine

the friction and wear behavior of magnetron-sputtered diamondlike carbon (MS DLC) and plasma-assisted, chemical-vapor-deposited

diamondlike carbon (PACVD DLC) films in sliding contact with 6-mm-diameter American Iron and Steel Institute (AISI) 440C stainless

steel balls. Unidirectional sliding friction experiments were conducted with a load of 5.9 N (600 g), a mean Hertzian contact pressure of

0.79 GPa (maximum Hertzian contact pressure of 1.2 GPa), and a sliding velocity of 0.2 m/s. The experiments were conducted at room

temperature in three environments: ultrahigh vacuum (vacuum pressure, 7×10 -7 Pa), humid air (relative humidity, -20 percent), and dry

nitrogen (relative humidity, <1 percent). The resultant films were characterized by scanning electron microscopy, energy-dispersive x-ray

spectroscopy, and surface profilometry. Marked differences in the friction and wear of the DLC films investigated herein resulted from the

environ-mental conditions. The main criteria for judging the performance of the DLC films were coefficient of friction and wear rote, which

had to be less than 0.3 and on the order of 10-6 mm3/N-m or less, respectively. MS DLC films and PACVD DLC films met the criteria in

humid air and dry nitrogen but failed in ultrahigh vacuum, where the coefficients of friction were greater than the criterion, 0.3. In sliding

contact with 440C stainless steel balls in all three em'ironments the PACVD DLC films exhibited better tribological performance (i.e., lower

friction and wear) than the MS DLC films. All sliding involved adhesive transfer of wear materials: transfer of DLC wear debris to the

counterpart 440C stainless steel and transfer of 440C stainless steel wear debris to the counterpart DLC film.

14. SUBJECT TERMS

Lubricants

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

18. SECU'RiTY CLASSIFICATION

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION

OF ABSTRACT

Unclassified

15. NUMBER OF PAGES

22

16. PRICE CODE

A03

20. LIMITATION OF AB:STHACT

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. Z39-18

298-102