Study on cavitation erosion behavior of nano-bainitic GCr15SiMo steels: Experiments and molecular dynamics simulations

The nano-bainitic steels were produced by a series of heat treatments applied to GCr15SiMo bearing steels. The microstructure, mechanical properties, and cavitation erosion behavior were investigated and compared with those of martensitic and annealed steels of the identical chemical composition. Furthermore, the cavitation erosion behavior was elucidated through molecular dynamics (MD) simulations to provide atomic-scale insights. The experimental results demonstrated that nano-bainitic steel exhibited exceptional cavitation erosion resistance due to its unique combination of high strength and toughness. After 840 min of cavitation erosion, the mean depth of erosion (MDE) was approximately 2.20 μm, merely 1/15 and 1/2 that of annealed steel (600 min) and martensitic steel (840 min). The complexity of the eroded surface products of nano-bainitic steel after 840 min of cavitation erosion was significantly lower than that of martensitic steel (840 min) and annealed steel (600 min). MD simulations revealed that the nano-water hammer caused by the collapse of cavitation bubble could reach extreme transient conditions, including pressure up to 30 GPa and temperature up to 5000 K on the nano-bainitic model surface, accompanied by extremely high shear stresses. The combined effect of these conditions resulted in a partial transformation of the crystal structure on the surface of the nano-bainitic model. This transformation contributed to the enhanced cavitation erosion resistance of the nano-bainitic steel.