Enhanced cavitation erosion resistance of FeCrNiTiAlNb multi-principal element alloy coatings via grain-boundary-phase engineering

Cavitation erosion (CE) in hydraulic turbine flow-passing components impedes hydropower efficiency and undermines carbon neutrality efforts. This work presents a grain-boundary-engineered FeCr₃₀Ni₂₅Al₅Ti₅Nb_x multi-principal element alloy coating that achieves breakthrough CE resistance through Nb-mediated microstructure control. The Nb2.6 specimen exhibited 1.35 mg cumulative mass loss after 20 h ultrasonic CE testing, which is 8.9 % of the conventional ZG04Cr13Ni5Mo steel and 17.9 % of the Nb-free counterparts. Microstructural analysis reveals that Nb addition refines BCC grains (24.3 ± 2.4 to 17.7 ± 1.2 μm), increases grain-boundary-decorated FCC phase fraction (up to 24.3 ± 3.5 %), and promotes Laves phase precipitation. These modifications mitigate stress concentration, restrict crack propagation via dislocation pinning, and enable coordinated deformation between BCC and FCC phases. This work establishes a grain-boundary engineering strategy for designing CE-resistant coatings, advancing sustainable hydropower and marine applications.