AFM	Atomic force microscope
COF	Coefficient of friction
EDX	Energy dispersive X-ray
PID	Proportional integral derivative
PVD	Physical vapor deposition
SEM	Scanning electron microscope
SPIP	Scanning probe image processor
XRD	X-ray diffraction
Nomenclature
R	Diameter of the ball (mm)
R	Radius of the ball (mm)
d	Worn area diameter of the ball (mm)
rwt	Wear track radius (mm)
wwt	Wear track width (mm)
Vb	Volume losses of ball (mm3)
Vd	Volume losses of disk (mm3)
WR	Wear rate (mm3/N m)
H	Hardness (GPa)
E	Elastic modulus (GPa)
E′	Effective elastic moduli (GPa)
F	Normal load (N)
Pmaks	Maximum contact pressure (GPa)
Ra	Arithmetic mean roughness of coatings (nm)
Sa	Surface average roughness (nm)
S	Sliding distance (m)
U	Sliding speed (m/s)
μm	Length (μm)
D	The crystallite sizes (nm)
K	Sherrer constant
β	Full-width at half maximum of XRD peaks
λ	Wavelength of the X-ray source (nm)
θ	Angle of diffraction peak (radian)
ε	Lattice strain
H3/E2	Modulation ratio