Multi-layer coating design architecture for optimum particulate erosion resistance

The hard particle, erosion resistance of multi-layer, magnetron-sputtered, physical vapor deposited (PVD), titanium nitride/titanium (TiN/Ti) coatings for protection of AM355 steel turbine components was investigated. Multi-layer coatings, of 25 μm total thickness, were deposited on AM355 substrates with variable numbers and thicknesses (equivalent to volume fractions) of the TiN and Ti layers. The coatings were eroded using glass beads, quartz and alumina media with particle velocities ranging from 75 to 180 m/s. Erosion performance was found to depend strongly on the TiN/Ti PVD coating multi-layer design architecture and the erosion conditions. The results showed that coatings with two layers, one of TiN, and a low volume fraction of metal gave optimal erosion performance against the alumina erodent, whereas coatings with 32 layers, (16 each of TiN and Ti), offered the best erosion performance against the glass beads. These results explain the variability of coating erosion performance described in the literature, and provide guidance in the design of optimal multi-layer coating systems for a range of particle erosion conditions.