Comparative study of electrochemical and impact wear behavior of TiCN, TiSiCN, TiCrSiCN, and TiAlSiCN coatings

The aim of this work was to investigate the electrochemical and repetitive impact wear behaviors of Cr- and Al-doped TiSiCN coatings in comparison with their TiCN and TiSiCN counterparts. The coatings were deposited by reactive DC magnetron sputtering of TiC, TiSiC, TiCrSiCN, and TiAlSiCN targets in a gaseous mixture of Ar + 15%N2. The structure, elemental and phase compositions of coatings were studied by means of X-ray diffraction, scanning electron microscopy, and glow discharge optical emission spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, elastic recovery, and adhesion strength. To evaluate their electrochemical characteristics, the coatings were tested in 1N H2SO4 and 0.9% NaCl solutions. The coatings were also subjected to a range of impact tests, first in air, and then in normal saline (to assess a tribocorrosion effect) and distilled water (to assess a hydrodynamic effect in liquid). The obtained results show that all the coatings, except the TiCN, exhibit similar mechanical properties but their failure modes (plastic deformation, brittle fracture or their combinations) during scratch tests are markedly different. The poorest dynamic impact performance of the TiCN coating in air, distilled water, and NaCl solution was attributed to both the imperfection of coating structure (micro-chips and “pin-holes”) and reduced mechanical properties. Although the TiSiCN coating possessed the highest hardness, its high wear led to a reduced impact resistance. The Cr-doped TiSiCN coating performed well in air, but rapidly failed during dynamic impact tests in normal saline due to corrosion reactions. The TiAlSiCN coating was the only one which sustained repetitive impact load for 105 cycles in air (maximal normal load of 1000 N), as well as in distilled water (neutral medium) and normal saline (corrosive medium) at 500 N.