DLC MULTILAYER COATINGS FOR WEAR PROTECTION

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.