Investigation a unique scratching of the failure mechanisms of the coatings with TiN thin layers deposited on 316L stainless steel

Starting from the finding that the coatings with TiN of the total hip prostheses femoral heads made of Ti-6Al-4V alloy have tendencies to wear (abrasive, adhesive or bio-tribo-corrosion), the paper has proposed to establish the failure mechanisms of these thin layers coatings. For economic reasons, the studies were made on TiN coatings on 316L stainless steel (SS 316L), steel with mechanical characteristics similar to the Ti-6Al-4V alloy. Three types of TiN coatings were made on cylindrical samples of SS 316L by the Pulse Laser Deposition (PLD) method. Depending on the number of deposition pulses, coatings with different thicknesses and harnesses were obtained. Since the failure of coatings is generally due to the failure of coating's adhesion to the substrate's material, the coating's adhesion was tested by single pass single indenter (SPSI) scratch tests to completely avoid the occurrence of the fatigue phenomenon that may occur in the case of multi-pass single indenter (MPSI) scratch test or multi-pass dual indenters (MPDI). The critical failure events of the three types of coatings were highlighted and commented, concluding that PLD coatings with 10000 and 20000 pulses are the ones that offer the most favorable perspectives from the coating – substrate adhesion point of view