Amorphous hydrogenated diamond-like carbon (DLC) coatings containing a
small amount of titanium have been deposited onto AISI 420 steel subs
trates by unbalanced magnetron sputtering. In order to make the diamon
d-like carbon coating adhere to the metal, four kinds of graded interl
ayers, i.e. Ti, TiN, TiCN and TiC, have been used, taking advantage of
the fact that the Ti layer adheres to the metal and DLC adheres to th
e TiC layer. The total thickness of the DLC coatings is 2.0 mu m. The
DLC coatings showed excellent properties, i.e. high microhardness valu
es (higher than 39 Hv (GPa)), excellent adhesion (Lc 10.0-11.0 kg), fr
iction coefficients against an Al2O3 ceramic ball being in the range 0
.05-0.3 and an extremely long wear lifetime. In addition, wear tracks
of the DLC coatings as well as wear scars of the sliding Al2O3 balls w
ere investigated with the help of optical microscopy and scanning elec
tron microscopy studies. Tribological studies of the DLC coatings with
other ball wear materials were also carried out. The results indicate
that the studied DLC coatings passes dramatically improved wear prote
ction properties as compared to e.g. high-quality TiN or TiC coatings.
The coatings were analysed using X-ray diffraction, infrared spectros
copy, Rutherford backscattering spectrometry and elastic recoil detect
ion.