0 0.1 0.2 0.3 0.40.5µ Temperature T r EP lubricant Mixture of EP lubricant and fatty acid EP lubricant reacts with the surfaces at temperatureT r FIGURE 8.55 Co-application of adsorption
Trang 1disulphide and dilauryl hydrogen phosphate By using these additives separately andtogether the effect of phosphorus, sulphur and phosphorus-sulphur on seizure load wasfound [109].
0 100
of practical machinery The IAE (Institute of Automotive Engineers) and IP (Institute ofPetroleum) 166 gear tests conducted with the same additives revealed that the phosphorus-based additive allowed the same seizure or failure loads for a much smaller concentrationthan the sulphur-based additive [109] The critical difference between the Timken test and thegear tests is the slide/roll ratio The Timken test involves pure sliding while the gear testsonly impose sliding combined with rolling It appears that the sulphur originated surfacefilms are more resistant to the shearing of pure sliding than films formed from phosphorousadditives
The chemistry of steel surfaces after lubrication by sulphur-phosphorus oils was also studied[109,110] Films found on wear scars formed under severe conditions, e.g the Timken test,consisted mostly of sulphur However, under milder load and lower slide/roll ratios, whichare characteristic for general machinery, it was found that phosphorus predominates in thewear scar films This pattern of film chemistry versus sliding severity is illustratedschematically in Figure 8.53
It can be seen from Figure 8.53 that a sulphur-phosphorus based lubricant providesconsiderable versatility in lubricating performance The sulphur is essential to preventseizure under abnormally high loads and speeds while phosphorus maintains low frictionand wear rates under normal operating conditions
Trang 2Low friction
property
critical
Anti-seziure property critical Phosphorus
Sulphur
Low
Phosphorous-sulphur composite films
Moderate High (pure sliding) Slide/roll ratio:
Load severity: Moderate
Temperature Distress
Temperature distress is a term used to describe high friction occurring over a relativelynarrow band of intermediate temperature in lubrication by an oil An example of this effect isshown in Figure 8.54 which illustrates the friction coefficient versus temperature resultsfrom a four-ball test where the lubricant tested is white oil with tributylphosphate [111].The tests were conducted at a relatively high contact stress of approximately 2 [GPa] and, toensure negligible frictional transient temperatures, at a very low sliding speed of 0.2 [mm/s].Friction, initially moderate at room temperature, rises to a peak between 100 - 150°C followed
by a sharp decline at higher temperatures This phenomenon is the result of a significantdifference between the desorption temperature of surfactants from the steel surface and thelowest temperature where rapid sacrificial film formation can occur In this test, thesurfactants were relatively scarce consisting only of impurities or oxidation products in thewhite oil In practical oil formulations, however, surfactants are carefully chosen so that thedesorption temperature is higher than the ‘start temperature’ of sacrificial film lubrication.The concept of wide temperature range lubrication which is achieved by employing intandem adsorption and sacrificial film lubrication is illustrated in Figure 8.55
It can be seen that when only the fatty acid is applied, the coefficient of friction is quite lowbelow a critical temperature and then sharply rises Conversely when the E.P additive (in anE.P lubricant) is acting alone, the coefficient of friction remains high below a critical
Trang 30 0.1 0.2 0.3 0.4
0.5µ
Temperature
T r
EP lubricant Mixture of EP lubricant and fatty acid
EP lubricant reacts with the surfaces at temperatureT r
FIGURE 8.55 Co-application of adsorption and sacrificial film lubrication to ensure a wide
temperature range of lubrication function [6]
Trang 4Speed Limitations of Sacrificial Film Mechanism
As discussed in this chapter, sacrificial films formed on severely loaded surfaces require somefinite period of time to reform between successive sliding contacts In most research it isassumed that the formation time is so short that it does not exert a significant limitation onlubricant performance It was found, for example, that E.P additives were effective in raisingthe maximum load before scuffing only at low sliding speeds [112] In low speed testsperformed under pure sliding using a pin-on-ring machine, when an E.P additive was
present, the scuffing load was increased by a factor of 2 compared to that of plain oil At
higher speeds the E.P additives had almost no effect on the scuffing load It is speculated that
at high speeds the sacrificial films did not form and as a result the E.P additives wereineffective
Tribo-emission From Worn Surfaces
Tribo-emission is a term describing the emission of electrons, ions and photons as a response
to friction and wear processes The mechanisms involved in tribo-emission are complex andnot known in detail [130] However, it is speculated that triboemission precedes and is evennecessary for tribochemical reactions to occur in the tribocontact The best researched is theemission of already mentioned low energy electrons (Figures 8.44 and 8.45), also calledexoelectrons One of the mechanisms proposed, involving tribo-emission of electrons, isdescribed below
During wear surface cracks are generated as a result of severe deformation of the wornsurface In general, when a crack forms there is an imbalance of electrons on opposite faces ofthe crack [e.g 126-128] This imbalance is particularly evident in ionic solids which arecomposed of alternating layers of anions and cations For example, when a crack develops inaluminium oxide, one side of the crack will contain oxide anions while the opposite sidewill contain aluminium cations The narrow gap between opposing faces of a crack causesformation of a large electric field gradient (electric field gradient is controlled by the distancebetween opposite electric charges) This electric field is sufficient to cause electron escapefrom the anions [128] It is believed that not all the electrons which escape from the anionsare collected by the cations on the opposing crack face This results in tribo-emission or therelease of electrons into the wider environment under the action of sliding Thephenomenon is schematically illustrated in Figure 8.56
In dry sliding tests under vacuum, ceramics exhibit a strong tribo-emission of electronsbecause of their ionic crystalline structure while metals reveal a lesser tendency since thehigh electron mobility in a metal tends to equalize electron distribution on either side of thecrack Tribo-emission also occurs during sliding in air or under a lubricant but the electronsare not easily detected as their path length in air is much shorter than that in vacuum Waterand possibly other gases or liquids may influence tribo-emission of electrons bychemisorption on the exposed surfaces of the crack about to release electrons Irradiation byhigh energy radiation such as gamma-rays appears to activate worn surfaces to significantlyraise the level of tribo-emission, the detailed physical causes of this phenomenon are stillpoorly understood [129]
Tribo-emission of positive and negative ions, as well photons, has been detected during wear
of ceramics in n-butane of various pressure [127] In this case the wear mechanism wasexplained in terms of gas discharge due to high electric field generated on the wear surfacewhen charges are separated The ionized gas molecules may then recombine generatingmolecules different from the original gas A completely different mechanism of tribo-emission was also suggested for a similar ceramic-diamond abrasive contact [130] Tribo-emission from MgO scratched by diamond was attributed to excited defects created byabrasion in the solid phase
Trang 5Crack formation Generation of Tribo-emission
electric field
+ + + +– –
– –
Strong electric field
Electron capture
Electron escape (diversion of electron caused by thermal vibration of anion and
cation) Cations
Anions
Figure 8.56 Schematic illustration of the mechanism of crack-induced tribo-emission.The tribo-emission accelerate chemical reactions such as oxidation or polymerization of thelubricant under boundary lubrication conditions [127] and is an example of mechanicalactivation The tribo-emission is beneficial if it promotes formation of wear and frictionreducing surface films but is harmful if these films or a lubricant are degraded to produce asludge or other forms of debris Therefore it is important to know whether the tribo-emission triggers the tribochemical reactions and whether these reaction products influencewear and friction characteristics
8.6 BOUNDARY AND E.P LUBRICATION OF NON-METALLIC SURFACES
Most of the discussion on boundary and E.P lubrication in this chapter refers to lubrication
of metallic surfaces Increased interest in the tribological applications of ceramics has resulted
in more research into boundary lubrication of ceramics, especially at elevated temperatures.Both E.P [131] and detergent-type additives [132] were found to form boundary lubricatinglayers on silicon nitride in the ‘four-ball’ tester EDX analysis revealed, however, than thetribochemical reactions on silicon nitride were different from those found on steel surfaceswhen the same detergent-type additives were used Since ceramics are less reactive thanmetals the effectiveness of typical adsorption and antiwear additives in many cases appears to
be lower for ceramic-ceramic contacts than for ceramic-metal contacts [133] Although asacrificial iron phosphate film was detected on the silicon nitride surface when it was slidagainst steel with vapour phase lubrication of oleic acid and TCP, the triboreaction took place
on the steel surface [133] When self-mated silicon nitride was lubricated by the same vapourphase much higher wear was recorded
On the other hand, boundary lubrication by sacrificial films of oxides and hydroxides is muchmore effective for ceramics than for metals [117] For example, silicon nitride can belubricated by thin layers of silicon oxide and alumina by alumina hydroxide formed in thetribocontact In contrast with E.P sacrificial films on metal surfaces, ceramic oxides andhydroxides do not require high temperatures to be generated
More information on lubrication of ceramics can be found in Chapter 16
Lubrication by chemical and physical interaction between an oil-based lubricant and a surface(usually metal) is essential to the operation of most practical machinery Four basic forms ofthis lubrication are identified: (i) the formation of an ultra-viscous layer close to the wornsurface, (ii) the shielding of an oxidized metal surface by a mono-molecular layer of adsorbedlinear surfactants, (iii) the separation of contacting surfaces by entrapped layers of finelydivided and perhaps amorphous debris and (iv) the suppression of metal to metal contact atextreme pressures by the temperature dependent formation of sacrificial films of corrosionproduct on worn metallic surfaces Each lubrication mechanism has certain merits anddisadvantages but they all contribute to the reduction of wear and friction under conditionswhere other lubrication mechanisms such as hydrodynamic and elastohydrodynamic
Trang 6lubrication are ineffective This is achieved by the addition of some relatively cheap andsimple chemicals to the oil It is possible to describe fairly precisely how a particular additivefunctions in terms of friction and wear control However, the prediction of lubricantperformance from chemical specification is still not possible and this constrains research totesting for specific applications This task remains a future challenge for research.
3 Lord Rayleigh (J.W Strutt), On the Lubricating and Other Properties of Thin Oily Films, Phil Mag J.
Science, 6th Series, Vol 35, 1918, pp 157-163.
4 W.B Hardy and I Doubleday, Boundary Lubrication - The Paraffin Series, Proc Roy Soc., London, Series A,
Vol 100, 1921, pp 550-574.
5 W.B Hardy and I Doubleday, Boundary Lubrication - The Temperature Coefficient, Proc Roy Soc., London,
Series A, Vol 101, 1922, pp 487-492.
6 F.P Bowden and D Tabor, The Friction and Lubrication of Solids, Part 1, Clarendon Press, Oxford, 1950.
7 D Tabor, Desorption or 'Surface Melting' of Lubricant Films, Nature, Vol 147, 1941, pp 609- 610.
8 W.C Bigelow, D.L Pickett and W.A Zisman, Oleophobic Monolayers, I Films Adsorbed from Solution in
Non-Polar Liquids, Journal of Colloid Science, Vol 1, 1946, pp 513-538.
9 C.O Timmons, R.L Patterson and L.B Lockhart, Adsorption of Carbon-14 Labelled Stearic Acid on Iron,
Journal of Colloid and Interface Science, Vol 26, 1968, pp 120-127.
10 K Tanaka, Molecular Arrangement in Thin Films of Some Paraffins, Mem Coll Sic Kyoto Imp Univ., Vol.
A23, 1941, pp 195-205.
11 J.M Cowley, Electron Diffraction by Fatty Acid Layers on Metal Surfaces, Trans Faraday Soc., Vol 44, 1948,
pp 60-68.
12 K.G Brummage, An Electron-Diffraction Study of the Structure of Thin Films of Normal Paraffins, Proc Roy.
Soc., London, Series A, Vol 188, 1947, pp 414-426.
13 K.G Brummage, An Electron-Diffraction Study of the Heating of Straight Chain Organic Films and its
Application to Lubrication, Proc Roy Soc., London, Series A, Vol 191, 1947, pp 243-252.
14 J.W Menter, Effect of Temperature on Lateral Spacing of Fatty Acid Monolayers on Metals - Electron
Diffraction Study by Transmission, Research (London), Vol 3, 1950, pp 381-382.
15 F.P Bowden, J.N Gregory and D Tabor, Lubrication of Metal Surfaces by Fatty Acids, Nature, Vol 156, 1945,
18 M Beltzer and S Jahanmir, Role of Dispersion Interactions Between Hydrocarbon Chains in Boundary
Lubrication, ASLE Transactions, Vol 30, 1987, pp 47-54.
19 P Studt, The Influence of the Structure of Isometric Octadecanols on their Adsorption from Solution on Iron
and Their Lubricating Properties, Wear, Vol 70, 1981, pp 329-334.
20 S Jahanmir and M Beltzer, An Adsorption Model for Friction in Boundary Lubrication, ASLE Transactions,
Vol 29, 1986, pp 423-430.
21 E Ando, Y Goto, K Morimoto, K Ariga and Y Okahata, Frictional Properties of Monomolecular Layers of
Silane Compounds, Thin Solid Films, Vol 180, 1989, pp 287-291.
22 H Okabe, T Ohmori and M Masuko, A Study on Friction-Polymer Type Additives, Proc JSLE Int Tribology Conf., 8-10 July 1985, Tokyo, Publ Elsevier, pp 691-696.
23 E.D Tingle, The Importance of Surface Oxide Films in the Friction and Lubrication of Metals, Part 2, The
Formation of Lubrication Films on Metal Surfaces, Trans Faraday Soc., Vol 326, 1950, pp 97-102.
Trang 724 F.P Fehlner and N.F Mott, Low Temperature Oxidation, Oxidation of Metals, Vol 2, 1970, pp 59-99.
25 A.W Batchelor and G.W Stachowiak, Some Kinetic Aspects of Extreme Pressure Lubrication, Wear, Vol.
108, 1986, pp 185-199.
26 R Dubrisay, Alteration of Metals by Organic Acids Dissolved in Non-Aqueous Liquids, Comptes Rendus,
Academie des Sciences, Vol 210, 1940, pp 533-534.
27 C.F Prutton, D.R Frey, D Turnbull and G Dlouhy, Corrosion of Metals by Organic Acids in Hydrocarbon
Solution, Industrial Engineering Chemistry, Vol 37, 1945, pp 90-100.
28 I.B Goldman, J.K Appeldoorn and F.F Tao, Scuffing as Influenced by Oxygen and Moisture, ASLE
Transactions, Vol 13, 1970, pp 29-38.
29 R.O Daniels and A.C West, The Influence of Moisture on the Friction and Surface Damage of Clean Metals,
Lubrication Engineering, Vol 11, 1955, pp 261-266.
30 D Godfrey, The Lubrication Mechanism of Tricresyl Phosphate on Steel, ASLE Transactions, Vol 8, 1965, pp.
1-11.
31 I.L Goldblatt and J.K Appeldoorn, The Antiwear Behaviour of Tricresylphosphate (TCP) in Different
Atmospheres and Different Base Stocks, ASLE Transactions, Vol 13, 1970, pp 203-214.
32 Y Kimura and H Okabe, Tribology, An Introduction, Publ Youkandou, Tokyo, Japan, 1982.
33 H Okabe, M Masuko and K Sakurai, Dynamic Behaviour of Surface-Adsorbed Molecules Under Boundary
Lubrication, ASLE Transactions, Vol 24, 1981, pp 467-473.
34 E.P Kingsbury, Some Aspects of the Thermal Desorption of a Boundary Lubricant, Journal of Applied Physics,
37 A Dyson, Scuffing, A Review, Tribology International, Vol 8, 1975, Part 1: pp 77-87, Part 2: pp 117-122.
38 H Blok, Les Temperatures de Surface dans des Conditions de Graissage sous Pression Extreme, Proc Second World Petroleum Congress, Paris, Vol 4, 1937, pp 151-82.
39 H Blok, The Flash Temperature Concept, Wear, Vol 6, 1963, pp 483-494.
40 A Dorinson and K.C Ludema, Mechanics and Chemistry in Lubrication, Elsevier Amsterdam, 1985, pp 469.
457-41 T.E Tallian, Discussion to ‘The Effects of Temperature and Metal Pairs on Scuffing’, M.W Bailey and A.
Cameron, ASLE Transactions, Vol 16, 1973, pp 121-131.
42 J.J Frewing, The Heat of Adsorption of Long-Chain Compounds and their Effect on Boundary Lubrication,
Proc Roy Soc., London, Series A, Vol 182, 1944, pp 270-285.
43 T.C Askwith, A Cameron and R.F Crouch, Chain Length of Additives in Relation to Lubricants in Thin Film
and Boundary Lubrication, Proc Roy Soc., London, Series A, Vol 291, 1966, pp 500-519.
44 W.J.S Grew and A Cameron, Thermodynamics of Boundary Lubrication and Scuffing, Proc Roy Soc., London,
Series A, Vol 327, 1972, pp 47-59.
45 O Beeck, J.W Givens and A.E Smith, On the Mechanism of Boundary Lubrication: I The Action of
Long-Chain Polar Compounds, Proc Roy Soc., London, Series A, Vol 177, 1940, pp 90-102.
46 R.S Fein, Operating Procedure Effects on Critical Temperatures, ASLE Transactions, Vol 10, 1967, pp
373-385.
47 H.J Carper, P.M Ku and E.L Anderson, Effect of Some Material and Operating Variables on Scuffing,
Mechanism and Machine Theory, Vol 8, 1973, pp 209-225.
48 J.C Bell, A Dyson and J.W Hadley, The Effect of Rolling and Sliding Speed on the Scuffing of Lubricated
Steel Discs, ASLE Transactions, Vol 18, 1975, pp 62-73.
49 G.H Kitchen, The Economics of Tribology, Proc Int Tribology Conference, Melbourne, The Institution of Engineers, Australia, National Conference Publication No 87/18, December, 1987, pp 424-427.
50 W.J.S Grew and A Cameron, Role of Austenite and Mineral Oil in Lubricant Failure, Nature, Vol 217, 1968,
pp 481-482.
51 F.G Rounds, The Influence of Steel Composition on Additive Performance, ASLE Transactions, Vol 15, 1972,
pp 54-66.
Trang 852 M.W Bailey and A Cameron, The Effects of Temperature and Metal Pairs on Scuffing, ASLE Transactions,
Vol 16, 1973, pp 121-131.
53 R.M Matveevsky, V.M Sinaisky and I.A Buyanovsky, Contribution to the Influence of Retained Austenite
Content in Steels on the Temperature Stability of Boundary Lubricant Layers in Friction, Transactions ASME,
Journal of Tribology, Vol 97, 1975, pp 512-515.
54 H Diergarten, J Stocker and H Werner, Erfahrungen mit dem Vierkugelapparat zur Beurteilung von
Schmierstoffen, Erdol und Kohle, Vol 8, 1955, pp 312-318.
55 K.H Kloos, Werkstoffpaarung und Gleitreibungsverhalten in Fertigung und Konstruktion, Fortschrittberichte
der VDI Zeitschriften, Reihe 2, 1972, pp 1-91.
56 A Begelinger, A.W.J de Gee and G Salomon, Failure of Thin Film Lubrication - Function-Orientated
Characterization of Additives and Steels, ASLE Transactions, Vol 23, 1980, pp 23-24.
57 K.-H Habig, P Feinle, Failure of Steel Couples Under Boundary Lubrication: Influence of Steel Composition,
Microstructure and Hardness, Transactions ASME, Journal of Tribology, Vol 109, 1987, pp 569-576.
58 A.J Groszek, Heats of Preferential Adsorption of Boundary Additives at Iron Oxide/Liquid Hydrocarbon
Interfaces, ASLE Transactions, Vol 13, 1970, pp 278-287.
59 F Hirano and T Sakai, The Chain Matching Effect on Performance of Mechanical Seals, Proc 9th Int Conf Fluid Sealing, BHRA, 1981, pp 429-444.
60 F Hirano, N Kuwano and N Ohno, Observation of Solidification of Oils under High Pressure, Proc JSLE Int Tribology Conf., 8-10 July, 1985, Tokyo, Japan, Elsevier, pp 841-846.
61 G.J Johnston, R Wayte and H.A Spikes, The Measurement and Study of Very Thin Lubricant Films in
Concentrated Contacts, Tribology Transactions, Vol 34, 1991, pp 187-194.
62 A Cameron and T.N Mills, Basic Studies on Boundary, E.P and Piston-Ring Lubrication Using a Special
Apparatus, ASLE Transactions, Vol 25, 1982, pp 117-124.
63 P Cann, H.A Spikes and A Cameron, Thick Film Formation by Zinc Dialkyldithiophosphate, ASLE
Transactions, Vol 26, 1986, pp 48-52.
64 D Mazuyer, J.M Georges and B Cambou, Shear Behaviour of an Amorphous Film with Bubbles Soap Raft Model, Proc 14th Leeds-Lyon Symp on Tribology, Interface Dynamics, Sept 1987, editors: D Dowson, C.M Taylor, M Godet and D Berthe, Elsevier, 1988, pp 3-9.
65 M Belin, J.M Martin, J.L Mansot, Role of Iron in the Amorphization Process in Friction-Induced Phosphate
Glasses, Tribology Transactions, Vol 32, 1989, pp 410-413.
66 J.M Martin, M Belin, J.L Mansot, H Dexpert and P Lagarde, FrictionInduced Amorphization with ZDDP
-an EXAFS Study, ASLE Tr-ansactions, Vol 29, 1986, pp 523-531.
67 J Dimnet and J.M Georges, Some Aspects of the Mechanical Behaviour of Films in Boundary Lubrication,
ASLE Transactions, Vol 25, 1982, pp 456-464.
68 I.N Lacey, G.H Kelsall and H.A Spikes, Thick Antiwear Films in Elastohydrodynamic Contacts Part 1:
Film Growth in Rolling/Sliding EHD Contacts, ASLE Transactions, Vol 29, 1986, pp 299-305.
69 I.N Lacey, G.H Kelsall and H.A Spikes, Thick Antiwear Films in Elastohydrodynamic Contacts Part 2:
Chemical Nature of the Deposited Films, ASLE Transactions, Vol 29, 1986, pp 306-311.
70 M.J Furey, The Formation of Polymeric Films Directly on Rubbing Surfaces to Reduce Wear, Wear, Vol 26,
1973, pp 369-392.
71 A Dorinson, Influence of Chemical Structures in Sulfurized Fats on Anti-Wear Behaviour, A S L E
Transactions, Vol 14, 1971, pp 124-134.
72 E.H Loeser, R.C Wiquist and S.B Twist, Cam and Tappet Lubrication, IV, Radio-Active Study of Sulphur in
the E.P film, ASLE Transactions, Vol 2, 1959-1960, pp 199-207.
73 V.N Borsoff and C.D Wagner, Studies of Formation and Behaviour of an Extreme Pressure Film, Lubrication
Engineering, Vol 13, 1975, pp 91-99.
74 R.B Campbell, The Study of Hypoid Gear Lubrication Using Radio-Active Tracers, Proc Lubrication and Wear Convention, Inst Mech Engrs Publ., London, 1963, pp 286-290.
75 C.F Prutton, D Turnbull and G Dlouhy, Mechanism of Action of Organic Chlorine and Sulphur Compounds in
Extreme-Pressure Lubrication, J Inst Petroleum, Vol 32, 1946, pp 90-118.
76 K.G Allum and E.S Forbes, The Load Carrying Mechanism of Some Organic Sulphur Compounds - An
Application of Electron Microprobe Analysis, ASLE Transactions, Vol 11, 1968, pp 162-175.
Trang 977 B.A Baldwin, Relationship Between Surface Composition and Wear, An X-Ray Photo-Electron Spectroscopic
Study of Surfaces Tested with Organo-Sulphur Compounds, ASLE Transactions, Vol 19, 1976, pp 335-344.
78 H.A Spikes and A Cameron, Additive Interference in Dibenzyl Disulphide Extreme Pressure Lubrication,
ASLE Transactions, Vol 17, 1974, pp 283-289.
79 W Davey, Some Observations on the Mechanism of the Development of Extreme Pressure Lubricating
Properties by Reactive Sulfur in Mineral Oil, J Inst Petroleum, Vol 31, 1945, pp 154-158.
80 T Sakurai and K Sato, Study of Corrosivity and Correlation Between Chemical Reactivity and Load
Carrying Capacity of Oils Containing Extreme Pressure Agent, ASLE Transactions, Vol 9, 1966, pp 77-87.
81 M Masuko, N Naganuma and H Okabe, Acceleration of the Thermal Reaction of Sulfur with Steel Surface
Under Increased Pressure, Tribology Transactions, Vol 33, 1990, pp 76-84.
82 A Dorinson and K.T Ludema, Mechanics and Chemistry in Lubrication, Elsevier, Amsterdam, 1985, pp 307.
255-83 J.L Lauer, N Marxer and W.R Jones, Ellipsometric Surface Analysis of Wear Tracks Produced by Different
Lubricants, ASLE Transactions, Vol 29, 1986, pp 457-466.
84 J Ferrante, Exoelectron Emission from a Clean, Annealed Magnesium Single Crystal During Oxygen
Adsorption, ASLE Transactions, Vol 20, 1977, pp 328-332.
85 E.A Gulbransen, The Role of Minor Elements in the Oxidation of Metals, Corrosion, Vol 12, 1956, pp 61-67.
86 K Meyer, Physikalich-Chemische Kristallographie, Gutenberg Buchdruckerei, 1977, German Democratic Republic.
87 Cz Kajdas, On a Negative-Ion Concept of EP Action of Organo-Sulfur Compounds, ASLE Transactions, Vol 28,
1985, pp 21-30.
88 T.F Gesell, E.T Arakawa and T.A Callcott, Exoelectron Emission During Oxygen and Water Chemisorption
on Fresh Magnesium Surface, Surface Science, Vol 20, 1970, pp 174-178.
89 A.W Batchelor, A Cameron and H Okabe, An Apparatus to Investigate Sulfur Reactions on Nascent Steel
Surfaces, ASLE Transactions, Vol 28, 1985, pp 467-474.
90 K Meyer, H Berndt and B Essiger, Interacting Mechanisms of Organic Sulphides with Metallic Surfaces and
their Importance for Problems of Friction and Lubrication, Applications of Surface Science, Vol 4, 1980, pp.
154-161.
91 O.D Faut and D.R Wheeler, On the Mechanism of Lubrication by Tricresylphosphate (TCP) - The Coefficient of Friction as a Function of Temperature for TCP on M-50 Steel, Vol 26, 1983, pp 344-350.
92 R.O Bjerk, Oxygen, An "Extreme-Pressure Agent", ASLE Transactions, Vol 16, 1973, pp 97-106.
93 M Masuko, Y Ito, K Akatsuka, K Tagami and H Okabe, Influence of Sulphur-base Extreme Pressure Additives on Wear Under Combined Sliding and Rolling Contact, Proc Kyushu Conference of JSLE, Oct., 1983,
pp 273-276 (in Japanese).
94 D.H Buckley, Oxygen and Sulfur Interactions with a Clean Iron Surface and the Effect of Rubbing Contact in
these Interactions, ASLE Transactions, Vol 17, 1974, pp 201-212.
95 E.P Greenhill, The Lubrication of Metals by Compounds Containing Sulphur, J Inst Petroleum, Vol 34, 1948,
pp 659-669.
96 J.J McCarroll, R.W Mould, H.B Silver and M.C Sims, Auger Electron Spectroscopy of Wear Surfaces, Nature
(London), Vol 266, 1977, pp 518-519.
97 K Date, Adsorption and Lubrication of Steel with Oiliness Additives, Ph.D thesis, London University, 1981.
98 M Tomaru, S Hironaka and T Sakurai, Effects of Some Oxygen on the Load-Carrying Action of Some
Additives, Wear, Vol 41, 1977, pp 117-140.
99 T Sakai, T Murakami and Y Yamamoto, Optimum Composition of Sulfur and Oxygen of Surface Film Formed
in Sliding Contact, Proc JSLE Int Tribology Conf., July 8-10, Tokyo, Japan, Elsevier pp 655-660.
100 B.A Baldwin, Wear Mitigation by Anti-Wear Additives in Simulated Valve Train Wear, A S L E
Transactions, Vol 26, 1983, pp 37-47.
101 E.S Forbes, The Load Carrying Action of Organic Sulfur Compounds, a Review, Wear, Vol 15, 1970, pp 87-96.
102 E.S Forbes and A.J.D Reid, Liquid Phase Adsorption/Reaction Studies of Organo-Sulfur Compounds and
their Load Carrying Mechanism, ASLE Transactions, Vol 16, 1973, pp 50-60.
103 D Godfrey, The Lubrication Mechanism of Tricresylphosphate on Steel, ASLE Transactions, Vol 8, 1965, pp.
1-11.
Trang 10104 E.H Loeser, R.C Wiquist and S.B Twist, Cam and Tappet Lubrication, Part III, Radio-Active Study of
Phosphorus in the E.P Film, ASLE Transactions, Vol 1, 1958, pp 329-335.
105 P.A Willermet, S.K Kandah, W.O Siegl and R.E Chase, The Influence of Molecular Oxygen on Wear
Protection by Surface-Active Compounds, ASLE Transactions, Vol 26, 1983, pp 523-531.
106 M Kawamura, K Fujita and K Ninomiya, Lubrication Properties of Surface Films Under Dry Conditions,
Journal of JSLE., International Edition, No 2, 1981, pp 157-162.
107 P.V Kotvis, L Huezo, W.S Millman and W.T Tysoe, The Surface Decomposition and Extreme-Pressure
Tribological Properties of Highly Chlorinated Methanes and Ethanes on Ferrous Surfaces, Wear, Vol 147,
1991, pp 401-419.
108 D Ozimina and C Kajdas, Tribological Properties and Action Mechanism of Complex Compounds of Sn(II)
and Sn(IV) in Lubrication of Steel, ASLE Transactions, Vol 30, 1987, pp 508-519.
109 K Kubo, Y Shimakawa and M Kibukawa, Study on the Load Carrying Mechanism of Sulphur-Phosphorus Type Lubricants, Proc JSLE Int Tribology Conf., 8-10 July, 1985, Tokyo, Japan, Elsevier, pp 661-666.
110 A Masuko, M Hirata and H Watanabe, Electron Probe Microanalysis of Wear Scars of Timken Test Blocks
on Sulfur-Phosphorus Type Industrial Gear Oils, ASLE Transactions, Vol 20, 1977, pp 304-308.
111 R.M Matveevsky, Temperature of the Tribochemical Reaction Between Extreme-Pressure (E.P.) Additives
and Metals, Tribology International, Vol 4, 1971, pp 97-98.
112 G Bollani, Failure Criteria in Thin Film Lubrication With E.P Additives, Wear, Vol 36, 1976, pp 19-23.
113 T.A Stolarski, A Contribution to the Theory of Lubricated Wear, Wear, Vol 59, 1980, pp 309-322.
114 C.N Rowe, Role of Additive Adsorption in the Mitigation of Wear, ASLE Transactions, Vol 13, 1970, pp.
179-188.
115 S.C Lee and H.S Cheng, Scuffing Theory Modelling and Experimental Correlations, Transactions ASME,
Journal of Tribology, Vol 113, 1991, pp 327-334.
116 H.A Spikes and A Cameron, A Comparison of Adsorption and Boundary Lubricant Failure, Proc Roy Soc.,
London, Series A, Vol 336, 1974, pp 407-419.
117 S.M Hsu, Boundary Lubrication: Current Understanding, Tribology Letters, Vol 3, 1997, pp 1-11.
118 W.F Bowman and G.W Stachowiak, A Review of Scuffing Models, Tribology Letters, Vol 2, No 2, 1996, pp.
113-131.
119 K Meyer, H Berndt and B Essiger, Interacting Mechanisms of Organic Sulphides With Metallic Surfaces
and Their Importance for Problems of Friction and Lubrication, Applications of Surface Science, Vol 4, 1980,
pp 154-161.
120 S Mori and Y Shitara, Chemically Active Surface of Gold Formed by Scratching, Applied Surface Science,
Vol 68, 1993, pp 605-607.
121 A.W Batchelor and G.W Stachowiak, Model of Scuffing Based on the Vulnerability of an
Elastohydrodynamic Oil Film to Chemical Degradation Catalyzed by the Contacting Surfaces, Tribology
Letters, Vol 1, No 4, 1995, pp 349-365.
122 A Douglas, E.D Doyle and B.M Jenkins, Surface Modification for Gear Wear, Proc Int Tribology Conference, Melbourne, The Institution of Engineers Australia, National Conference Publication No 87/18, December,
1987, pp 52-58.
123 M.A Keller and C.S Saba, Catalytic Degradation of a Perfluoroalkylether in a Thermogravimetric
Analyzer, Tribology Transactions, 1998, Vol 41, pp 519-524.
124 D.J Carre, Perfluoroalkylether Oil Degradation: Inference of FeF3 Formation on Steel Surfaces Under
Boundary Conditions, ASLE Transactions, Vol 29, 1986, pp 121-125.
125 Y Hoshi, N Shimotamai, M Sato and S Mori, Change of Concentration of Additives Under EHL Condition
-Observation by Micro-FTIR, The Tribologist, Proc Japan Society of Tribologists, Vol 44, No 9, 1999, pp
736-743.
126 B Rosenblum, P Braunlich and L Himmel, Spontaneous Emission of Charged Particles and Photons During
Tensile Deformation of Oxide-Covered Metals Under Ultrahigh Vacuum Conditions, Journal of Applied
Physics, Vol 48, 1997, pp 5263-5273.
127 K Nakayama and H Hashimoto, Triboemission, Tribochemical Reaction and Friction and Wear in Ceramics
Under Various N-Butane Gas Pressures, Tribology International, Vol 29, 1996, pp 385-393.
Trang 11128 C Kajdas, Physics and Chemistry of Tribological Wear, Proceedings of the 10th International Tribology Colloquium, Technische Akademie Esslingen, Ostfildern, Germany, 9-11 January, 1996, Volume I, (editor: Wilfried J Bartz), publ Technische Akademie Esslingen, 1996, pp 37-62.
129 Y Enomoto, H Ohuchi and S Mori, Electron Emission and Electrification of Ceramics During Sliding, Proceedings of the First Asia International Conference on Tribology, ASIATRIB'98, Beijing, publ Tsinghua University Press, 1998, pp 669-672.
130 J.T Dickinson, L Scudiero, K Yasuda, M-W Kim and S.C Langford, Dynamic Tribological Probes: Particle
Emission and Transient Electrical Measurements, Tribology Letters, Vol 3, 1997, pp 53-67.
131 R.S Gates and S.M Hsu, Silicon Nitride Boundary Lubrication: Effect of Phosphorus-Containing Organic
Compounds, Tribological Transactions, Vol 39, 1996, pp 795-802.
132 R.S Gates and S.M Hsu, Silicon Nitride Boundary Lubrication: Effect of Sulfonate, Phenate and Salicylate
Compounds, Tribology Transactions, Vol 43, 2000, pp 269-274.
133 W Liu, E.E Klaus and J.L Duda, Wear Behaviour of Steel-on-Si3N4 and Systems with Vapor Phase
Lubrication of Oleic Acid and TCP, Wear , Vol 214, 1998, pp 207-211.
Trang 12Specialized solid substances can also be used to confer extremely high wear resistance onmachine parts The economics of manufacture are already being transformed by the greaterlifetimes of cutting tools, forming moulds, dies, etc The wear resistant substances may beextremely expensive in bulk, but when applied as a thin film they provide an economicaland effective means of minimizing wear problems The questions of practical importanceare: what are the commonly used solid lubricants? What distinguishes a solid lubricant fromother solid materials? What is the mechanism involved in their functioning? What are themethods of application of solid lubricants? What are the wear resistant coatings and methodsfor their deposition? In this chapter the characteristic features of solid lubricants and basicsurface treatments are discussed.
9.2 LUBRICATION BY SOLIDS
In the absence of lubrication provided by liquids or gases, most forms of solid contact involveconsiderable adhesion between the respective surfaces Strong adhesion between contactingsurfaces nearly always causes a large coefficient of friction because most materials resist shearparallel to the contact surface as effectively as they resist compression normal to the contactface However, some materials exhibit anisotropy of mechanical properties, i.e failure occurs
at low shear stresses, resulting in a low coefficient of friction at the interface Anisotropy ofmechanical properties, or in simple terms, planes of weakness, are characteristic of lamellarsolids If these lamellae are able to slide over one another at relatively low shear stresses thenthe lamellar solid becomes self lubricating This mechanism is schematically illustrated inFigure 9.1