Atomic Erosion Behavior and Influence Mechanism of (CoCrFeMn)_1–<i>x</i>Ni_<i>x</i> High-Entropy Alloy Coating on Fracturing Pump Valves During Stimulation Operation

The CoCrFeMnNi high-entropy alloy is widely regarded as a highly promising coating for enhancing the erosion resistance of fracturing pump valves, owing to its outstanding overall properties. This study employs molecular dynamics simulations to compare and analyze the wear and erosion resistance mechanisms of (CoCrFeMn)_1-<i>x</i>Ni_<i>x</i> coatings with varying Ni ratios (0.2, 0.4, 0.6, 0.8) under nanoindentation, scratch, and impact conditions at a microscopic scale. The findings indicate that as the proportion of Ni increases under the three simulation conditions, the coating exhibits more dislocation locks, an HCP phase structure, and shear bands. These factors collectively enhance the material's surface hardness, wear resistance, and plastic recovery. Nonetheless, this is not universally applicable. When the indentation and scratch depth are greater than 20 Å, the (CoCrFeMn)_0.4Ni_0.6 coating benefits from robust metal bonds and a stable lattice structure, leading to fewer wear atoms and subsurface defects, thus exhibiting superior erosion resistance. These conclusions serve as a theoretical foundation for the selection of (CoCrFeMn)_1-<i>x</i>Ni_<i>x</i> coatings in practical fracturing operations.