EXTREME-PRESSURE LUBRICANT ADDITIVES. by Andrew Allan Bayles A thesis submitted for

169 Pages·2015·3.85 MB·English

1
KINETICS OF
- EXTREME-PRESSURE LUBRICANT ADDITIVES.
by
Andrew Allan Bayles
A thesis submitted for the degree of
DOCTOR OF PHILOSOPHY
of the University of London
and also for the
DIPLOMA OF MEMBERSHIP of the IMPERIAL COLLEGE
SEPTEMBER 1975
Lubrication Laboratory, Department of Mechanical Engineering,
Imperial College of Science and Technology,
London, SW7 2BX.
ii
ABSTRACT
This thesis has investigated the kinetics of the reaction
between steel surfaces and a simple E.P. oil, Dibenzyl Disulphide in
cetane, by examining the friction-temperature characteristics of the
metal-lubricant system on a variable, slow-speed, ball-on-triplane
machine.
A theoretically derived relationship linking sliding speed
with transition temperature has been confirmed experimentally and
values for the Activation Energy of the reaction and the Heat of
Adsorption of the additive to the surface have been obtained. A
mechanism is proposed to explain the observed kinetic behaviour.
The function of the E.P. film in preventing scuffing failure
at high speed has been examined from a kinetic stand point.
It is suggested that lubricant failure is governed by a
balance between the rate of reaction of the additive with the surface
and the rate of removal of the E.P. film from the surface.
iii
ACENOWT7DGEMENTS
The author is greatly indebted to Professor Cameron for his
guidance and sunervision, throughout the course of this nroject; to Mr.
Reg Dobson for his encouragement and invaluable technical assistance;
and to the members of the laboratory, who have assisted in numerous ways.
Sincere thanks are also due to Ruston, Paxman Diesels Ltd.,
and to the Lubrication Engineers Ltd., for providing the funds which
made this study possible.
iv
CONTENTS
Page
Title page
Abstract ii
Acknowledgements iii
Contents iv
List of Figures vii
Nomenclature xi
Chapter 1 Literature Review 1
1.1 Introduction 1
1.2 Extreme-Pressure Lubrication 2
1.3 Composition of the E.P. film 4
1.4 Investigations into E.P. Activity 6
1.5 Effects of Load, Speed and Temperature on
E.P. film formation 8
1.6 Mechanism of E.P. Action 11
1.7 Kinetics of the Reaction between E.P. Additives
and Iron Surfaces 15
1.8 Concept of the Research Programme 19
Chanter 2 Annaratus and Preliminary Investigations 20
2.10 Introduction 20
2.20 Apparatus 20
2.21 Materials 28
2.22 Experimental Procedure 29
2.30 Accuracy 30
Page
2.40 Results and Discussion - I 39
2.41 E.P.M.A. Introduction 39
2.42 Procedure . 41
2.43 Limitations of Results 42
2.44 Results 42
2.50 Results and Discussion - II 49
2.51 Powder Analysis 53
2.60 Conclusions 56
3
Chapter The Effects of Sliding Sneed on the Lubrication of
EN 31 Steel by Dibenzyl Disulphide 57
3.10 Introduction 57
3.20 aperimental 57
3.21 Speed Range 57
3.22 Heating Rate 58
3.23 Materials and Lubricant 58
3.30 Accuracy 65
3.40 Results 65
3.50 Discussion 68
3.60 Conclusions 74
4
Chapter The Effects of Additive Concentration on the
Lubrication of EN 31 Steel 75
4.10 Introduction 75
4.20 Results 84
4.30 Discussion - I 85
4.40
Discussion - II 89
4.50 Discussion - III 92
vi
Page
4.60 Conclusions 95
Chapter 5 Investigations into High-Speed Failure 97
5.10 Introduction 97
5.20 Lubricant Failure 97
5.30 Apparatus 103
5.31 Materials 104
5.32 Procedure 104
5.33 Accuracy 107
5.40 Results 107
5.50 Discussion 108
5.51 The Mechanism of Scuffing Failure 115
Chapter 6 Conclusions and Suggestions for Future Work 118
6.10 Conclusions 118
6.11 Slow Speed Work (Chapters 2,3,and 4) 118
6.12 High Speed Tests (Chapter 5) 119
6.20 Future Work 120
Appendix 122
References 124
vii
LIST OF FIGURES
Chapter 2 Page
2.1 Ball-on-triplane machine. 21
2.2 Ball-on-triplane machine, schematic diagram. 22
2.3 Ball-on-Triplane Machine: Peg Positions. 23
2.4 Peg-cup. 25
2.5 Heater. 26
2.6 Drive System. 26
2.7 Typical Pen Recorder Trace.DBDS on EN 31 steel. 27
2.8 Friction vs Temperature. DBDS on EN 58 steel, 31
1 r.p.m.
2.9 Friction vs Temperature. DBDS on EN 31 steel, 32
1 r.p.m.
2.10 Friction vs Temperature. DBDS on EN 31 steel, 33
1 r.p.m. Heat rate dependence.
2.11 Friction vs Time. Pure Cetane on EN 31 steel, 34
1 r.p.
2.12 Friction vs Temperature. Unlubricated EN 31 35
steel,1 r.p.m. (16.7N load).
2.13 Friction vs Temperature. Unlubricated EN 31 36
steel,1 r.p.m. (62.3N load).
2.14 Unlubricated EN 31 steel,1 r.p.m. Reversibility 37
Trace.
2.15 Friction vs Temperature. DBDS on EN 58 steel 38
1 r.p.m. Reversibility of friction with
temperature.
viii
Page
2.16 Electron Probe Microanalyser. 40
2.17 E.P.M.A. Count across track rubbed in DBDS
solution.
2.18 Back-Scattered Electron Image. (B.E.I.). 44
2.19 Absorbed Electron Image. (A.E.I.). 44
2.20 X-ray Image. (X.R.I.). 44
2.21 E.P.M.A. Count outside track, rubbed in DBDS 45
solution.
2.22 E.P.M.A. Count across track rubbed in pure 46
cetane.
2.23 Debye-Scherrer Powder Method: 52
(a ) Relation of film to specimen and incident beam.
(b ) Appearance of film after exposure.
2.24 Friction vs Film Thickness Reproduced from (73). 55
Chapter 3
3.1 Friction vs Temperature. 1% DBDS solution on
1
EN 31 steel ; /50 r.p.m. 59
3.2 Friction vs Temperature. 1% DBDS solution on
1
EN 31 steel, /10 r.p.m. 59
3.3 Friction vs Temperature. 1% DBDS solution on

1
EN 31 steel /3 r.p.m. 60
3.4 Friction vs Temperature. 1% DBDS solution on

EN 31 steel, 1 r.p.m. 60
3.5 Friction vs Temperature. 1% DBDS solution on

EN 31 steel, 3 r.p.m. 61
3.6 Friction vs Temperature. 1% DBDS solution on
1
EN 31 steel; 3 /3 r.p.m. 62
ix
Page
3.7 Friction vs Temperature. 1% DBDS solution on
1
En 31 steel , 6 /2 r.p.m. 63
3.8 Friction vs Temperature. 1% DBDS solution on
EN 31 steel , 10 r.p.m. 64
3.9 Logi° Sliding Speed vs 1/TT EN 31 steel. 69
3.10 Significance of Activation Energy, 70
1
3.11a Logi() Reaction vs /T, Mild steel. 72
1
b Logio Reaction vs /T,Stainless steel. 72
Chapter 4
4.1 Dependence of Friction Transition on Sliding
Speed. 2% DBDS. 76
4.2 Dependence of Friction Transition on Sliding
Speed. 0.5% DBDS, 77
4.3 Dependence of Friction Transition on Sliding
Speed. 0.2% DBDS, 78
4.4 Logi° Sliding Speed vs 1/TT, 2% DBDS. 80
4.5 Logic) Sliding Speed vs 1/TT, 0.5% DBDS. 81
4.6 Logic) Sliding Speed vs 1/TT, 0.2% DBDS. 82
1
4.7 Combined Logic) Sliding Speed vs /TT.Effect
of Concentration. 83
1
4.8 Logi° Rate Constant vs IT (reproduced from (34)). 86
4.9 Friction vs Temperature. 1% DBDS + 1% Toluene on
1
EN 31 steel. /10 r.p.m. 94
Chapter 5 Page
5.1 Four-Ball Apparatus. 102
5.2 Dependence of Scuff load on Additive
Concentration. 105
5.3 Dependence of Scuff load on Sliding Speed. 106
5.4 Rate vs Concentration, Dyphenyl Disulphide in
White Oil (reproduced from (38)), 113
5.5. Film thickness vs Sliding Speed, DBDS in White
Oil (reproduced from (38)), 113