Abstract: An experimental study is presented on the wear and failure of initial coarse-grained and modified ultrafine-grained Ti-6Al-4V alloy with a TiN protective coating, subjected to high-speed dynamic erosion by solid corundum particles with an average size of 109 μm in an air flow at a speed of 150 m/s and an erosion time of 30, 60, 180, 300 and 600 s. The experimental results are used to determine the erosive wear rate and the shear area percentage, as well as to measure the worn layer depth and erosion-induced changes in microhardness and structure of the alloy near the coated and uncoated surface. It is shown that all alloy samples are prone to wear and failure under the given high-speed erosion conditions, but their behavior is closely related to the erosion time and the structure of the substrate. The protective coating deposited onto the surface of ultrafine-grained Ti-6Al-4V titanium alloy significantly reduces the erosive wear rate compared to a similar coating on as-received coarse-grained alloy.