Friction and wear behaviour of TiN/Au, TiN/MoS2 and TiN/TiCN/a-C:H coatings

TiN/Au, TiN/MoS2, and TiN/TiCN/a-C:H coatings were deposited on M2 high speed steel using unbalanced magnetron sputtering systems. Hardness measurements and scratch tests were performed to monitor the mechanical properties. Reciprocating multi-pass and pin-on-disc wear tests were carried out to compare their friction and wear properties. The results indicated that the soft or lubricate layer on the TiN hard coatings reduced the friction and resulted in a lower shear stress being developed at coating/substrate interfaces. This favoured a higher scratch critical load compared with that for simple TiN coating. Failure mechanisms are discussed according to the examination of the response of the microstructure through the fractured cross-section of the scratch tracks. The friction behaviour as a function of the applied load was explored. TiN/Au and TiN/TiCN/a-C:H coatings show superior endurance in the reciprocating multi-pass test, whilst TiN/MoS2 and TiN/TiCN/a-C:H coatings provide better wear resistance in the pin-on-disc wear test.