Hydrocarbons - Technische Akademie Esslingen High...

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Unformatted text preview: Technische Akademie Esslingen High Temperature Lubrication via Hydrocarbon Vapors T, A. BLANCHET, D. M. HOLMES and W. G. SAWYER Rensseiaer Polytechnic Institute, Troy, USA fit a 11th International Colloqulum 13 - 15 January “an Industrial and Automotive Lubrication The ability of directed streams of three representative hydrocarbon gases - acetylene Czllz, ethylene CZH4, and ethane C2H5 - to provide extended duration lubrication to high temperature sliding contacts via surface deposition of pyrolytic carbon has been demonstrated. One order and twu order-ohnagnitude reductions of friction coefficient and wear rate of self-mated silicon nitride sliding contacts can be realized by this technique. The capacity of these gases to provide 'adequale' lubrication at iiiin temperature is illustrated through a mapping of the normal load I temperature I precursor flowrate space over which reduced friction may be maintained. Acetylene was the most effective precursor for pyrolytic carbon deposition, providing adequate lubrication over the broadest range of normal load I temperature I flowrate combinations, while ethane was the least effective. The boundary of regions of adequate lubrication represent the locus of contact conditions with equal rates of lubricous carbon deposition and removal removal by wear. The shape of this boundary, as explored in the mapping study, supports a proposed model in which the removal rate is proportional to the product of normal load and sliding speed while the deposition rate is proportional to the product of precursor flowrale and an Arrhenius temperature dependence. 1 . INTRODUCTION At temperatures below 350°C conventional lubrication strategies have been demonstrated and employed both repeatedly and reliably. Howwer. at more extreme temperatures the number of options to the design or lubrication engineer is significantly limited. Solid lubricants. lubricating powders, vapor phase lubrication. and gas phase lubrication greatly extend the operational range of tribological applications to well beyond the 350T threshold otherwise posed by the thermal capabilities of commercially available fluid lubricant basestocks. The limited range of thermal stability of existing fluid lubricants, and the difficulty in replenishing predeposited solid lubricant films as they inevitably wear away during operation, leaves vapor phase lubrication as a promising methodology for numerous high temperature extended duration bearing applications. Vapor phase lubrication has been successfully applied over a wide range of materials and temperatures. and has been surveyed recently by Rao iii. Vapor Phase Lubrication Smith, Furey. and Kajdas [2} have successfully lubricated concentrated ptn-on-disk sliding contacts of self~mated alumina through the tribopolymerization of monomers such as vinyl octadecyl ether. diallyl phthallate and lauryl methacrylate. The tribological contact experienced an initial maximum Henzian contact pressure of 3.5 GPa. sliding speed of 25 ants. modest background temperature of 145°C, and a sliding distance of 500m. A continuous nitrogen gas stream with vaporited monomers directed into the contact region was initiated to to 15 seconds prior to the initiation of loading and sliding, presumably to generate a polymer film prior to the onset of wear. At a monomer delivery temperature of 165°C Vinyl octadecyl ether was found to provide a 99% reduction in pin wear volume and a friction reduction of 38%, with coefficients of friction as low as 31-050, as compared to tests performed in a nitrogen gas enVironment under an identical background temperature, normal load. and sliding speed. 2285 Graham and Klaus had previously demonstrated the ability of tricresyl phosphate (TCP) and tributyl phosphate (TBP) vapors delivered to MSG bearing steel sliding surfaces to produce polymeric films capable of providing lubrication at higher temperatures of 370'C [3]. Hanyaloglu, Graham, et al. lubricated IN 800. IN 825. and MN 400 superalloys in reciprocating contacts with a vapor delivery of tri-aryl phosphate ester (TAP). The tribological contact conditions were an extremely modest average Hertzian contact pressure of 0.66 MPa, sliding speed of 12.7 crnls. background temperature of 500°C. and a typical sliding distance of 450m. Friction coefficients of u-0.0Z and u~0.03 were found for MN 400 and IN 800 respectively, and in both cases no wear of the base alloy was detected [4] Profilometric analysis , however. revealed wear of the lubricous surface films formed by these vapors. It should be addressed that these solid lubricating films may be generated through reactions of vapor with the base alloy. Cyclic formation and removal of such surface films may gradually consume the contacting bodies as a chemical wear mechanism. especially if film formation is aggressive. Also, due to the modest contact pressures employed, it remains unknown whether the surface films formed are able to endure concentrated contacts more typical of bearing applications. Hanyaloglu and Graham [5] have since expanded this work to temperatures of GOO'C tor SiAlONISiAlON and SiAIONImst iron sliding interfaces. Carbamemu Ga: Phase Lubrication The ability to provide and continuously replenish Iubricous arbon deposits through pyrolysis of directed hydrocarbon feed streams, which drastically reduce both sliding friction and Wear, has been successfully demonstrated by Lauer et al, in concentrated (p> l GPa) contacts at temperatures of up to soon: [6-9]. An example of this lubrimtion performance is shown in figure 1, where a one order-oI-magnitude reduction in friction and a two order-of- magn'itude reduction in wear volume are realized in a sell—mated sliding contact of silicon nitride at SZO'C. Barniclt. Blancth and Sawyer [10] subsequently demonstrated the applicability of this lubrication technique over a broad range of materials including ceramics, nickel superatloys, and steels. Pinvon-d'tsk sliding tests of self-mated couples were performed at SZO'C in an atmosphere purged with 3 literslminute of nitrogen. With a directed acetylene admixture supplied to the contact at 0.2 literslminute. Fricrion coefficients of less than it ~ 0.08 were recorded for all metal alloys tested - AISI M50. 52100, 440C and 1018 steel, as well as K- Monel (500) and Kastalloy C276. Friction coefficients of less than it a- 0.10 were found for all engineering ceramics tested - alumina, siliwn nitride, tungsten carbide, and zirconia. As the contacting bodies are not reactants in the pyrolytic generation of surface films, this lubrication technique does not pose the a corresponding chemical wear mechanism. In addition to acetylene, the utility of ethylene, carbon monoxidelhydrogen mixtures. and even combustion exhaust gas (though to a lesser extent) in providing lubrication to high temperature sliding and rolling contacts has similarly been demonstrated [8,9,11,12]. Previous works [1 1.12] have shown that 'adequate' lubrication. as indicated during experiment by low friction. requires a favorable balance of the deposition rate of solid carbon compared to the removal rate of this carbon through wear. Mapping the locus of combinations of normal load. temperature, and gas flow rate at which transitions from 'adequate' lubrication [u<0.l) to 'inadcquate' lubrication (u>0.5 typically) occurred enabled the dependencies of rates of carbon formation and removal on contact conditions to be examined. For example. it was shown that deposition rate increased linearly with admixture flowrate and had an Arrhenius dependence on temperature. while the removal rate increased linearly with normal load. Though not investigated experimentally in these works [11,12], it was hypothesized that removal rate (per unit time) also increases linearly with sliding speed. The ability for increasing sliding speed to induce transitions from adequate to inadequate lubrication was verified by Sawyer and Blanchct [13] in an investigation of the high- temperature traction behavior of such replenishable pyrolytic carbon deposits in concentrated combined rolllslide contacts using a Wedeven Associates WAM-l test machine. In addition to parameters such as normal load. sliding speed, temperature, and precursor gas flow rate, the type of precursor gas employed certainly affects the potential for adequate lubrication. A study was therefore undertaken in which three similar hydrocarbon gases with various carbon bond saturations were investigated. Acetylene (C132), ethylene (C254). and ethane (C235) have triple. double and single carbon-carbon bonding. respectively. Existing methodologies, described above, Were applied to map the fraction of the normal loadltemperaturelflow rate space over which each of the three hydrocarbon feed gases possesses the capacity for adequate lubrication. 2. EXPERIMENTAL The pln-on-dislt tribometer is comprised of two nested chambers. The inner chamber contains the contacting pin and dislt specimens, self-mated silicon nitride in this investigation. as well as a precursor admixture line. a nitrogen gas line, and an electric resistance lrvater. The flat disk is mounted on top of a drive spindle, wlrrle the hemispherically-tipped (r=l.6rnm) pin is contained within a holder located at the end of a cantilevered arm. The purged outer chamber contains and blankets the inner chamber from laboratory air. This tribometer is capable of continuous operation to ambient temperatures of SZO‘C or higher. The pin holder arm is hinged, which allows for a dead weight load to dictate the contact normal force. An AC motor controller monitors and maintains a constant disk spindle speed. The temperature of the test environment is monitored using a thermocouple located at the center of the disk surface. This thermocouple also provides feedback to the temperature controller which drives the resistance heaters located in the inner chamber. Four strain gauges are mounted to the base of the pin holder arm. They are used to measure the tangential loads on the cantilever resulting from friction forces in the comma. Connected to this trfbometer and strain gauge bridge is a computer controlled data acquisition system which monitors the strain gauge bridge voltage at an acquisition rate of 10 km. These values are then convened into friction coefficients, and a time-averaged value representing each consecutive ten-second period is recorded to a datafile. Sliding motion produces a circular wear track on the disk surface, as well as a wear scar on the pin. The diameter of the circular wear scar formed on the hemispherically-tipped pin can be measured post-test by optical microscopy, and used to calculate pin wear volume. 2286 The mapping of boundaries separating regions of adequate lubrication (u<0.i) and inadequate lubrication (p>0.5, typically) for each gas required the detection of transitions in friction coefficient induced during excursions in the studied test variables: normal load. sliding speed, and temperature. Sliding speed was held constant in these studies at 4.4cmls. Excursions were made slowly, so that friction coefficients recorded instantaneously approximate steady‘state behavior. Tests were initiated under conditions known a priori to provide adequate lubrication, with low friction and wear rate. and excursions in contact conditions were made until transitions to high friction were noted. By inducing transitions in the direction from adequate to inadequate lubrication, wear-induced damage and alteration of the surfaces during the slow excursions is minimized. A typical transition is shown below in figure 2. Mapping was performed in three modes: constant temperature; constant load; and constant flow rate. In each mode. numerous excursion tests were run to determine the locus of transition combinations of the non—constant parameters defining the boundary between adequate and inadequate lubrication. 3. RESULTS The test variables under consideration in this study are: temperature: normal load; admixture gas flowrate; and hydrocarbon admixture gas species. The experimental program was run in three different series: constant temperature; constant normal load; and constant llowrate, In figures 3-5 data points plotted represent combinations of the test variables causing transition from adequate to inadequate lubrication, found using techniques described in the experimental section. Tests run to investigate the dependencies of adequate lubrication on load and l'lowrate involved holding the temperature constant at SIO’C and finding transitions from adequate lubrication to inadequate lubrication over a range of normal loads from IN to 8N. For each load. a test was started at a sufficiently high flowrate to ensure initially adequate lubrication and low friction. Subsequently, flowrate was gradually reduced until a sharp increase in friction signified transition to inadequate lubrication. The results of this constant temperature lest series are shown with both acetylene and ethylene plotted on the same scatter plot in figure 3. On this plot the regions of adequate lubrication lie above the least square regression lines. It is clear that acetylene gas, which has a lower carbon bond saturation. can proVide adequate lubrication over a larger range of normal loads than ethylene for any given admixture flowrate. Tesu run to investigate the dependencies of adequate lubrication on temperature and llowrate involved holding the normal load constant at BAN. Each test was started at a sufficient combination of flowrate and temperature to ensure initially adequate lubrication and low friction. Subsequently. temperature was gradually reduced until a sharp increase in friction signified transition to inadequate lubrication. This procedure was repeated for various flowrates. The results of these constant load test series are shown with both acetylene and ethylene plotted on the same scatter plot in figure 4. on this plot the regions of adequate lubrication lie above theregression curves. ft is clear that acetylene gas, which has a lower carbon bond saturation, provides adequate lubrication over a broader range of combinations of flowrate and temperature than ethylene. Tests run to investigate the dependencies of adequate lubrication on temperature and normal load involved holding the admixtur- flowrate constant, while finding combinations of temperature an 5 normal load that induce transition from adequate to inadequat- lubrication. Due to the effectiveness of acetylene (relative to ethylene) in depositing pyrolytic carbon. constant flowrates of 0.1 llmin for acetylene and 1.3 llmin for ethylene were used so that transitions could be mapped over the same range of normal load and temperature. Each test was started at a sufficient combination of normal load and temperature to ensure initially adequate lubrication and low friction. Subsequently. temperature was gradually reduced until a sharp increase in friction signified transition to inadequate lubrication. This procedure was repeated for various nornral loads. The results of this test series are shown with both acetylene and ethylene plotted on the same scatter plot in figure 5. On this plot the regions of adequate lubrication lie below the regression curves. The loci of transition combinations of normal load and temperature for these twa gases overlap under the given test conditions. indicating that acetylene has the capacity to provide adequate lubrication Over the same range ul normal load and temperature as ethylene with a flowrate of only 15% that required for ethylene. Though also capable of providing adequate lubrication. experiments with ethane as a feed gas for pyrolytic carbon deposition and high temperature lubrication proved difficult. As shown in figure 6 at a temperature of SZO'C and a low load of 2.0!. a flow rate in excess of 2.5 llmin is required for adequate lubrication and low friction (peat). This represents. respectively, a one and two order-of-magnitude increase. respectively, in required flowrates for adequate lubrication when compared to ethylene and acetylene admixtures at the same temperature and load. Normal loads higher than IAN and temperatures 10“ er than SZO'C. as used in mapping the performance of acetylene and ethylene. would require even higher ethane flow rates. As such high hydrocarbon flow rates posed potential experimental difficulties, the mapping of ethane performance over a similar temperature I normal load I flow rate space was not pursued. 4. DISCUS SION This study demonstrated the deposition lubricous graphitic carbon from three different hydrocarbon feed gases on silicon nitride sliding surfaces at high temperature, capable of maintaining low friction coefficients (p e 0,1) and greatly reduced Wear rate (in some cases over two order-of-magnitude reduction) for extended durations. Pyrolytic carbon deposition was confirmed byRaman spectroscopy. with spectra demonstrating the characteristic disorder 151:3) and graphitic (spz) bonding peaks, centered at relative wavenunibers of approximately 1350 and 1580 itcrn‘l respectively, as shown in the example spectrum in figure 7. The range of contact conditions over which each of thee hydrocarbon gases can provide adequate lubrication varied greatly. with acetylene demonstrating the most broad effectiveness and ethane the least. The adequate lubrication of sliding contacts via in situ pyrolytic decomposition of directed hydrocarbon admixtures is believed to exist when the deposition rate of lubricous carbon exceeds the removal rate of this carbon. A proposed model [11,12] representing the net rate of change of carbon on the surface, OCIBt, is aCIateafexp(-EalRTi-bvrn, (eq.1) which includes the admixture flowrate (f), the ambient temperature (T). the sliding velocity (V), and the normal load (fin). The right hand side of this equation subtracts the removal rate of carbon (second term) from the deposition rate (first term). This difference is the net rate (volume per unit time) of carbon accumulation on the surface of the specimen. The constants. a and b. are coefficients for the deposition and removal terms respectively. The deposition rate is assumed to have an Arrhenius temperature dependence described by activation energy £3, with universal gas constant represented by R. Each gas precursor type may be characterized by a deposition coefficient a and activation energy for pyrolysis Ea. it can be shown that the removal coefficient b is the specific wear rate of pyroly‘tic carbon from the sliding surface, which may not vary among the three different hydrocarbon precursors, Transitions from adequate lubrication (BCIat > 0} to inadequate lubrication (aCIat < 0) are signified, as previously described. by sharp increases in friction coefficient. At transition (acrat = 0) the the deposition and removal rates balance. and can be equated. afexp(-EalRT) = bvrn lea-2) The coefficients a and b can be grouped into a transition constant Cyrans (= b I a) which, as a. should be specific for each precursor gas. Clrans = u' I Vin)exp(-Ea I RT) 3' (eq. 3) Any combination of contact conditions (f, F", T, V) which yields a value of the right hand side of eq. 3 equal to Ctrans should represent a transition condition, falling on the boundary between adequate and inadequate lubrication. This formulation agrees with the linear relationship between transition admixture flowrate and normal load observed at constant temperaturefligure 3). The Arrhenius description of temperature dependence by the proposed model can be checked by taking the natural logarithm of eq. 3 and rearranging it into a slope~intercept form where Y=In(V En I f). x=(t IRT). MW Fn 1!} = -Ea (1 ’RT) - lfllctransl (CQ- 4) 2287. For either gas (acetylene or ethylene) the constant flowrate and the constant normal load transition data. when plotted in such an X-Y fashion [figure 8). fall along straight lines of equal slope indicating that the Arrhenius temperature dependence proposed by the model is applicable. The constant flowrate and constant normal load data furthermore superimpose along the same line, with the constant temperature data clustering about a point on that line. indicating that the normal load and flowrate dependencies proposed in the model also hold, The adequate lubrication regime lies below these regression lines and it is again clear that the acetylene can provide adequate lubrication over a wider range of contact conditions. The relative difficulty previously mentioned in using ethane as a feed gas for pyrolytic carbon deposition at not is. of course. not beyond thermodynamic explanation. in the proposed model. it is assumed that the Gibbs free energy change AG for the pyrolysis reaction is negative. Activation of the forward reaction must overcome barrier height IEa , while activation of the reverse reaction faces a greater barrier height (E;l -AG) > Ea. In the proposed model it is also assumed that the magnitude of AG is sufficiently large. and activation barrier for the reverse reaction therefore sufficiently large, that the reverse reaction occurs at a neglible rate relative to the pyrolysis reaction, In such a case. the temperature dependence of the lubrication mechanism is sufficiently described by the Arrhenius representation. Over the range of temperatures tested, this appears to be the case for acetylene and ethylene. The activation energies for acetylene and ethylene, as expressed in these experiments. can be estimated from the slopes of linear data sets in figure 8 as l5a = 67 2 5 and 43 2 3 ltJIrnol respectively. Using tabulated thermochemical data, the free energy changes for the pyrolysis of acetylene and ethylene at SZO‘C can be approximated as roughly AG: -l60 and -too ltJlmol. respectively [14}. The magnitude of these Gibbs free energy changes are large relative to the activation energy, and should indeed cause the reverse reaction to be of negligible concern. For ethane. however. the free energy change during pyrolysis at 520'C is only roughly AG: ‘20 kJImol. small compared to the activation energy barrier expeaed for this pyrolysis reaction. Furthermore. AG is a function of temperature, and in the case of ethane pyrolysis becomes positive at temperatures not far below SOO'C. The difficulties in lubricating contacts by pyrolytic carbon from ethane feed gases can be understood in these terms. Also. it should be noted that the magnitude of Gibbs free energy decrease for the pyrolysis of acetylene decreases with increasing temperature, with AG eventually becoming positive. The Arrhenius temperature dependence within the proposed model is not expected to hold when the magnitude of Gibbs free energy decrease for pyrolysis becomes small relative to the activation energy. Furthermore. over certain temperature ranges the various hydrocarbon feed gases candidates for continuously replenished lubricous pyrolytic carbon supply to beating contacts may face thermodynamic limitations, 5. CLOSING REMARKS The ability of directed streams of three representatiw hydrocarbon gases to provide extended duration lubrication to high temperature sliding contacts via surface deposition of pyrolytic carbon has been demonstrated. Acetylene. with its carbon-carbon triple bond, was the most effective precursor for pyrolytic carbon deposition, providing adequate lubrication (1,141.1) over the broadest range of normal load I temperature I flowrate combinations. Ethane. having single-bonded carbon- carbon. proved least effective. fn addition to this new information concerning the effect of hydrocarbon precursor unsaturation. the mapping study also provided further support to a proposed model for the dependence of the lubrication mechanism on normal load. temperature, and precursor gas flowrate. Studies of the additional elfects of sliding and rolling speed and contact geometry on the lubrication mechanism have stnce been initiated. 6. ACKNOWLEDGMENTS This work was supported in part by the National Science Foundation Young Investigator Program under Grant No. CMS- 9157596. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views 01‘ the National Science Foundation. The authors also wish to acknowledge partial support of this work by a Graduate Student Researchers Program (6531’) fellowship awarded to one of the authors [WGS) [mm the NASA Langley Research Center. REFERENCES l. Rao, A; Vapor-Phase Lubrication: Application-Oriented Development. Lubrication Engineering 52 (1996) 856-862. 2.. Sllnllh. J.C.: Furey. M'..l.: Kajdas. C.: An Exploratory Study of Vapor-Phase Lubrication oi Ceramic by Monomers. Wear 181- 183 (1995) 531-593. 3. Graham. E.E.; Klaus. E.E.: Lubrication from the Vapor Phase at High Temperature. ASLE Transactions 29 (1986) 229- 234. 4. Hanyaloglu. B.P.; Graham. E.E.; Oreskovic, T.; Hajj. C.G.: Vapor Phase Lubrication of High Temperature Alloys. Lubrication Engineering 51 (1995) 503-508. 5. Hanyaloglu. BI; Graham. E.E.: Vapor Phase Lubrication oi Ceramic. Lubrication Engineering 50 (1994) 814 - 820. 6. Lauer, M...- Bunting. 15.6.: High Temperature Solid Lubricntion by Catalytically Generated Carbon. Tribology Transactions 34 (1988) 338449. 7. Laucr. J'.I_.,- Dwyer. S.R.: Tribochemical Lubrication of Ceramics by Carbonaceous Vapors. Tribology Transactions 34 (1991) 521-528. B. Lauer, 1.1.; Vlcelt, BL: Sargent. 8.: Wear Reduction by Pyrolytic Carbon on Tribosurlaces. Wear 162-164 (1993) 493' 507. 9. Iauer, J.L.; Blanchet. T.A.; Vlcek, B.L.; Sargent. B.: Lubrication of Steel Rolling and Sliding Contacts by Deposits of Pyrolyzed Carbonaceous Gases. Surlace and Coatings Technology 62 (1993) 399-405. 10. Barnick. N.J.: Blanchet. T.A.: Sawyer. W.G.: High Temperature Lubrication oi Various Ceramics and Metal Alloys via Directed Hydrocarbon Feed Gases. 'acceptcd [or publication in Wear. 11. Blanchet. I.A.; Iauer, J.L.; Liew, Y.F.; Rhee, 5.1.; Sawyer, W.G.: Solid Lubrication by Decomposition 0! Carbon Monoxide and Other Gases. Surlace and Coatings Technology. 68159 (1994) 446-4 52. 12. Sawyer, W.G..' Blanchet. '1'.A.; Calabrese. 5.1.: Lubrication ol Silicon Nitride in a Simulated Turbine Exhaust Gas Environment. Tribology Transactions 40(1997) 374-380. 13. Sawyer, W.G.; Blanchet. T.A.: High Temperature Lubrication 0! Combined Rollinglsliding Contacts via Directed Hydrocarbon Gas Streams. I'acceptecl lor publication in Wear. 14. Holmes. D.M.; Comparison of Acetylene, Ethylene, and Ethane as Gaseous Precursors for High Temperature Lubrication by Continuously Replenished Graphite Deposits. Master ol ScieHCe Thesis. Rensselaer Polytechnic Institute. Troy, NY. (1997). '1788 0'7 nitrogen only 0.6 (L5 0.6 0.3 friction coefficient (u) 0.2 0.1 nitrogen with acetylene 0.0 0 10 20 3O 40 50 60 70 80 sliding distance 011) 1, Friction coellicient 0! a sell-mated silicon nitride sliding contact at SZO'C in a nitrogen environment with and without a directed acetylene admixture lor pyrolytic carbon deposition. decreasing temperature —-—————--v———I> friction coefficient (u) -4 -3 -2 - I O 1 2 3 4 time (minutes) 2. Friction coelficient oi a sell-mated silicon nitride sliding contact in the presence of a directed Stream of acetylene at 0.15 limin (normal load 3.4N, sliding speed 4.4cmls) as temperature is gradually reduced with increasing time. Alter being reduced to 470'C, transition to high friction is observed. 1.4 I ethylene (CIH‘) adequate lubfitation 1.2 Oacetylene (Cit-i2) ' admixture flowrate (iitersfminute) . 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 3.0 Normal Load (N) 3. Combinations oi admixture flowrate and normal load at which transition from adequate to inadequate lubrication is noted for sliding contacts provided with acetylene and ethylene at a constant temperature of SZO'C and sliding speed oi 4.1km“. 2289 2.0 I ethylene (CzH‘l El acetylene (cle) 1.5 I adequate lubrication 1.0 0.5 admixture flowrate (liters/minute) 0.0 330 400 420 440 460 480 500 520 ambient temperature (“Cl 4. Combinations of admixture ilowrate and temperature at Which transition irom adequate to inadequate lubrication is noted for sliding contacts provided with acetylene and ethylene at a constant normal load ol 2.4N and sliding speed of 4.4cmls. 8.0 v ethylene KIM.) 1.3 Ilrm'n 6/ ‘ v 7-0 v acetylene (CIHI) 0.2 llmin 3/ ,_ 6.0 35 ‘D ID 2 5.0 ‘E E ‘6 c 4.0 3.0 2.0 380 400 420 440 460 480 500 520 ambient temperature 1°C) 5. Combinations of normal load and temperature at which transition lrom adequate to inadequate lubrication is noted lor sliding contacts provided with acetylene and ethylene at _a constant admixture I‘lowrate. A constant flow rate of O._2 llmin is used [or acetylene. and 1.3 llmin for ethylene. Sliding speed 4.401115. 0.3 — Ethane Csz E 0.2 .11 .2 ‘3 3 C .9 E on —-————-|> 2.5 literslminute 2.6 liters/minute 0.0 __l.__.__.._l... t —'l 5 ~10 - 5 0 5 10 1 5 time (minutes) 6. Friction coeliicient of a sell-mated silicon nitride sliding contact (temperature szo‘c. normal load 2.4N. sliding speed 4.4cmls) in the presence of a directed stream or ethane as precursor flowrate is gradually reduced with increasing time. Alter being reduced to 2.5 llmin, transition to high lriction is observed. 2290 l 5 l Intensity 1080 1260 1440 1620 Relative Wavenumber Rcm'| 7‘ Microlocused Raman spectrum taken from the pin wear scar. following lubrication by a directed stream ol acetylene. displaying disorder and graphiu'c peaks at roughly [350 and 1580 Rcm'1 characteristic ol lubricous pyrolytic carbons Constant arnhient temperature normal load admixture Howrah acetylene ethylene n (Jlmoll VF If -I O N 0J6 0J3 030 1rnr .1o31mow) 8. Summary plot of combinations of normal load. temperature, and admixture (low rate at which transition [tom adequate to inadequate lubrication is noted for sliding contacts provided with acetylene and ethylene at a sliding speed ol 4.4cmrs. Choice ol axes to facilitate evaluation of proposed model Note, admixture [lowrates have been converted lrom volume per time to moles per time. 2291 ...
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Hydrocarbons - Technische Akademie Esslingen High...

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