Micro-abrasive wear of PVD duplex and single-layered coatings

A micro-abrasive wear test has been used to evaluate the wear resistance of duplex coatings, consisting of plasma nitriding followed by PVD coating. Two duplex coatings were investigated: TiAlN and TiN. Single-layered TiAlN and TiN coatings were also tested to evaluate the effect of the duplex treatment on wear resistance. Prior to wear testing, coating properties were evaluated by hardness, scratch testing and surface profilometry. The best micro-abrasion resistance was shown by the duplex TiAlN coating, followed by single-layered TiAlN, duplex TiN and single-layered TiN coatings. The duplex treatment was effective in increasing the micro-abrasive wear resistance of its single-layered counterpart, since plasma nitriding prior to coating deposition increased the load support for the hard PVD coatings. The choice of the PVD coating also has a significant influence on the micro-abrasion resistance, with the more oxidation resistant TiAlN having a wear rate less than that of TiN. The results also indicate that coating debris acts as an additional source of abradant particles in the SiC slurry, leading to higher abrasive wear in the substrate. The harder the coating debris, the more severe the abrasive wear in the substrate is.