Ultra-thin multilayered erosion resistant Ti/TiN coatings with stress absorbing layers

Abstract

In this high speed era, several machine components are operated at high speeds and at high temperatures. Machine components such as gas turbine compressor blades and vanes are exposed to high speed dust particles. Consequently, engine performance deteriorates and in extreme cases catastrophic accidents can happen. In order to protect these engine components, ultra-thin multilayered erosion resistant Ti/TiN coatings (thickness ~9–10 μm) with stress absorbing layers were developed using magnetron sputtering. Stress absorbing metallic layers were introduced to control the internal stress and also to maintain balanced ductile and brittle nature of the coating. Ultra-thin (3–4 nm) metal/ceramic bilayers provided high number of interfaces and ultra-small grain sizes. Erosion resistance performance of the developed coatings and also bare Ti6Al4V substrates was tested according to the ASTM-G76-13 standard at 400 °C. Tests were conducted with three different erodent speeds of 30, 60 and 100 m/s at four different impinging angles 90°, 60°, 45° and 30°. The average erosion rate ratios between Ti6Al4V substrate and optimized coating were 74, 13 and 12 for the erodent speeds of 30, 60 and 100 m/s, respectively. Influence of the substrate on the coating performance was also studied. Morphological, elemental and spectral analyses of the erosion scar were also probed. Structural stability, mechanical properties and erosion resistance performance of the optimized film were tested after 100 h annealing in air and vacuum at a temperature of 400 °C. Erosion resistant performance of the optimized film was unaffected after 100 h annealing.