Table 1 Chemical compositions, mechanical and structural properties, and surface roughness parameters of the DLC coatings as used in this study.

From: Interplay of mechanics and chemistry governs wear of diamond-like carbon coatings interacting with ZDDP-additivated lubricants

Label

Composition (at%)

Young’s modulus E (GPa)

Hardness H (GPa)

Density ρ (g cm−3)

sp3 C \({p}_{{{sp}}^{3}}\) (%)

C

H

a-C:H

80

20

259

27

2.07

-

a-C

>99

<1

287

24

2.34

31

ta-C(51)

>99

<1

493

51

2.77

62

ta-C(66)

>99

<1

572

66

2.91

73

ta-C(78)

>99

<1

625

78

3.01

79

Label

RMS after running-in

 

height \({h}_{{{{\rm{rms}}}}}\) (nm)

slope \({h}_{{{{\rm{rms}}}}}^{{\prime} }\) (-)

 

Cylinder

Disc

Composite

Cylinder

Disc

Composite

a-C:H

5.0  ±  0.7

6.7 ± 1.3

8.4 ± 1.0

0.051 ± 0.015

0.087 ± 0.043

0.104 ± 0.032

a-C

13.4 ± 3.9

26.5 ± 0.1

29.8 ± 1.4

0.072 ± 0.002

0.131 ± 0.005

0.150 ± 0.004

ta-C(51)

3.9 ± 1.3

9.0 ± 2.0

9.8 ± 1.5

0.025 ± 0.002

0.054 ± 0.028

0.060 ± 0.020

ta-C(66)

3.8 ± 0.6

9.1 ± 0.4

9.9 ± 0.4

0.044 ± 0.010

0.078 ± 0.009

0.089 ± 0.008

ta-C(78)

10.9 ± 0.8

10.4 ± 4.3

15.3 ± 2.5

0.099 ± 0.013

0.080 ± 0.015

0.128 ± 0.012

  1. The densities ρ and percentages of sp3 carbon atoms \({p}_{{{{{\rm{sp}}}}}^{3}}\) are estimated from Young’s modulus using empirical formulae suggested by Ferrari and co-workers45,46. The reported RMS heights \({h}_{{{{\rm{rms}}}}}\) and slopes \({h}_{{{{\rm{rms}}}}}^{{\prime} }\) are average values measured inside the wear tracks of DLC-coated cylinders and discs after running-in (800 cycles for ta-C(78) and 2000 cycles for the others). The mathematical definitions of the RMS heights and slopes are available in Supplementary Note 1. The composite RMS slopes are defined as \(\scriptstyle\sqrt{{({h}_{{{{\rm{rms}}}},{{{\rm{cylinder}}}}}^{{\prime} })}^{2}+{({h}_{{{{\rm{rms}}}},{{{\rm{disc}}}}}^{{\prime} })}^{2}}\). The numbers after the ± signs are standard deviations.
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