The effect of a deposited soft thin metallic film on friction properties of a hardened steel substrate has been investigated experimentally and theoretically. The dependency of the film thickness and contact load on the static friction coefficient is presented. The experimental observations show that deformation of the film in contact was plastic, thereby confirming the assumption of the theoretical calculation. The effect of the film thickness on the contact area has been analyzed. A model for calculating the static friction coefficient of contacting rough surfaces in the presence of a soft thin film has been used. Results from the numerical calculations have been compared with the present static friction measurements performed on a pin on plate reciprocating apparatus. The rise in friction that occurs with increasing thickness for very thin films is discussed in detail. The calculated results, which predict the correct trend of the friction behavior from the present experiment, cover an extremely large range of $F/AnE$ from $10−12$ to $10−2,$ where three different dependencies of $F/AnE$ on the static friction coefficient can be identified. An investigation into the discrepancy between the calculated and experimental values for the static friction coefficient μ suggests that an accurate prediction of the magnitude of μ depends to a great extent on the level of accuracy in measuring the value of the constant ζ, the effective hardness of the film.

1.
Bowden, F. P., and Tabor, D., 1954, The Friction and Lubrication of Solids, Oxford University Press, Oxford.
2.
Finkin
,
E. F.
,
1969
, “
A Theory for the Effects of Film Thickness and Normal Load in the Friction of Thin Films
,”
ASME J. Lubr. Technol.
,
91
, pp.
551
556
.
3.
Dayson
,
C.
,
1971
, “
The Friction of Very Thin Solid Film Lubrication on Surface of Finite Roughness
,”
ASLE Trans.
,
14
, pp.
105
115
.
4.
Halling
,
J.
,
1975
, “
A Contribution to the Theory of Mechanical Wear
,”
Wear
,
34
, pp.
239
249
.
5.
El-Sherbiney
,
M. G. D.
, and
Halling
,
J.
,
1976
, “
The Hertizian Contact of Surfaces Covered With Metallic Films
,”
Wear
,
40
, pp.
325
337
.
6.
El-Sherbiney
,
M. G. D.
, and
Halling
,
J.
,
1977
, “
Friction and Wear of Ion-Plated Soft Metallic Films
,”
Wear
,
45
, pp.
211
220
.
7.
Halling
,
J.
,
1979
, “
Surface Coatings
,”
Tribol. Int.
,
10
, pp.
203
208
.
8.
El Shafei
,
T. E. S.
,
Arnell
,
R. D.
, and
Halling
,
J.
,
1983
, “
An Experimental Study on the Hertzian Contact of Surfaces Covered by Soft Metal Films
,”
ASLE Trans.
,
26
, pp.
481
486
.
9.
Ogilvy
,
J. A.
,
1993
, “
Predicting the Friction and Durability of MoS2 Coatings Using a Numerical Contact Model
,”
Wear
,
160
, pp.
171
180
.
10.
El-Sherbiney
,
M. G. D.
, and
Salem
,
F. B.
,
1979
, “
Initial Wear Rates of Soft Metallic Films
,”
Wear
,
54
, pp.
391
400
.
11.
El-Sherbiney
,
M. G. D.
, and
Salem
,
F. B.
,
1986
, “
Tribological Properties of PVD Silver Films
,”
ASLE Trans.
,
29
, pp.
223
228
.
12.
Kato
,
S.
,
Yamaguchi
,
K.
,
Marui
,
E.
, and
Tachi
,
K.
,
1982
, “
Friction Properties of a Surface Covered with a Soft Metal Film—Part 2: Analysis of Friction Between a Single Protuberance and a Surface
,”
ASME J. Lubr. Technol.
,
104
, pp.
39
45
.
13.
Nolle
,
H.
, and
Richardson
,
R. S. H.
,
1974
, “
Static Friction Coefficients for Mechanical and Structural Joints
,”
Wear
,
28
, pp.
1
13
.
14.
Paslay
,
P. R.
, and
Plunkett
,
R.
,
1953
, “
Design of Shrink-Fits
,”
Trans. ASME
,
75
, pp.
1199
1202
.
15.
Chang
,
W. R.
,
Etsion
,
I.
, and
Bogy
,
D. B.
,
1988
, “
Static Friction Coefficient Model for Metallic Rough Surfaces
,”
ASME J. Tribol.
,
110
, pp.
57
63
.
16.
Rabinowicz
,
E.
,
1967
, “
Variation of Friction and Wear of Solid Lubricant Films With Film Thickness
,”
ASLE Trans.
,
10
, pp.
1
9
.
17.
Tian
,
H.
, and
Saka
,
N.
,
1991
, “
Finite Element Analysis of an Elastic-Plastic Two Layer Half-Space: Normal Contact
,”
Wear
,
148
, pp.
47
68
.
18.
Derjaguin
,
B. V.
,
Muller
,
V. M.
, and
Toporov
,
Yu. P.
,
1975
, “
Effect of Contact Deformations on the Adhesion of Particles
,”
J. Colloid Interface Sci.
,
53
, pp.
314
326
.
19.
Muller
,
V. M.
,
Derjaguin
,
B. V.
, and
Toporov
,
Y. P.
,
1983
, “
On Two Methods of Calculation of the Force of Sticking of an Elastic Sphere to a Rigid Plane
,”
Colloids Surf.
,
7
, pp.
251
259
.
20.
Rabinowicz
,
E.
,
1971
, “
Contact Adhesion Between Solids in Vacuum: II. Deformation and Interfacial Energy
,”
J. Phys. D
,
11
, pp.
39
54
.
21.
Lozunskli, M. G., 1961, High Temperature Metallography, Pergamon, New York.
22.
Chang
,
W. R.
,
1997
, “
An Elastic-Plastic Contact Model for a Rough Surface With an Ion-Plated Soft Metallic Coating
,”
Wear
,
212
, pp.
229
237
.
23.
Stanley
,
H. M.
,
Etsion
,
I.
, and
Bogy
,
D. B.
,
1990
, “
Adhesion of Contacting Rough Surfaces in the Presence of Sub-Boundary Lubrication
,”
ASME J. Tribol.
,
112
, pp.
98
104
.
24.
Liu, Z., Neville, A. and Reuben, R. L., 2001, “Static Friction Modeling in the Presence of Soft Thin Metallic Films,” ASME Paper No. 462(2000)P/gga.
25.
Greenwood
,
J. A.
, and
Williamson
,
J. B. P.
,
1966
, “
Contact of Nominally Flat Surfaces
,”
Proc. R. Soc. London, Ser. A
,
295
, pp.
300
319
.
26.
McCool
,
J. T.
,
1987
, “
Relating Profile Instrument Measurements of the Functional Performance of Rough Surfaces
,”
ASME J. Tribol.
,
109
, pp.
264
270
.
27.
Hamilton
,
G. M.
,
1983
, “
Explicit Equations for the Stresses Beneath a Sliding Spherical Contact
,”
Proc. Inst. Mech. Eng., Part C: Mech. Eng. Sci.
197c
, pp.
53
59
.