Water droplet erosion mechanisms in rolled Ti–6Al–4V

Water impingement erosion of Ti-based parts is an issue encountered in many situations: aircraft body exposed to rain during flight, steam turbine blade, and inlet fogging used in gas turbines. The present work focuses on identifying the mechanisms of water droplet erosion of Ti–6Al–4V. Coupons of rolled Ti–6Al–4V have been exposed to high-speed water impingement erosion tests up to the advanced stage. Progressive cross-sectional polishing revealed both surface and sub-surface damage features at different scales. Qualitative observations and quantitative measurements were done on the eroded surface craters. Many micro-cracks along the erosion craters have been observed. The damage appeared to be dependent on the local microstructure morphology and the crystallographic texture of base material. A progressive mechanism for water droplet erosion during maximum erosion rate stage is proposed. It involves the nucleation of crack networks under the droplets impingements, cracks’ propagation and/or merging, tunneling or removal of large fragments of material due to linkage of cracks, water smoothing and, cyclically, nucleation of new sets of cracks.