Molecular Dynamics Modeling of Surface Microdamage Propagation and Evolution on Silicon Nitride Bearings Subjected to Nanoindentation

Microdamage is inevitable on the bearing surface during machining. To explore the propagation and evolution laws of microdamage on silicon nitride-bearing surfaces during loading and unloading, the point cloud data of actual microdamage are obtained based on three-dimensional (3D) reconstruction technology. A molecular dynamics (MD) model of a single-crystal silicon nitride Newtonian layer is constructed under loading and unloading with the help of the potential energy function generated by Deep Generator (DP-GEN). The multiscale local-overall indenter applied to the microdamage on silicon nitride-bearing surfaces is reconstructed, and its propagation and evolution trends are observed. The study revealed that at an atomic distance of 0.175 nm, the atomic radial distribution curve reached its peak value, and the g ( r ) value changed with the indentation depth as 2.0 nm > 1.7 nm > 1.4 nm, indicating the surface microdamage closed with the increase of loading depth. As the overall indentation area increases, the radial atomic distribution, amorphous atomic proportion, and load increase correspond to 3 times, 6 times, and 6 times that of the local indentation, respectively. This escalation intensifies the surface damage. Furthermore, with an increase in indentation depth, the microdamage exhibits a notable “self-healing” phenomenon. Additionally, the atoms surrounding the surface microdamage undergo amorphization and mismatch, accompanied by significant elastic recovery.