Nanoscale strengthening mechanism of Cr ion implantation and ion nitriding hybrid processes: nanoarchitectonics and simulation

Understanding the enhancement mechanism is fundamental for the precise application. This study employs molecular dynamics (MD) simulations of nanocrystalline Fe to investigate nanoscale strengthening mechanisms involved in Cr ion implantation and ion nitriding hybrid processes. Uniaxial tension and scratch simulations reveal that Young's modulus, strength, and wear resistance are enhanced and models treated with hybrid process exhibit superior performance compared to those treated with a single process. Beyond the inverse Hall-Petch effect and the reduction of potential energy, two new reinforcement mechanisms are discovered: 1) solutes impeding dislocation glide, inducing pinning effects and dislocation bowing, and 2) introduced defects facilitating dislocation nucleation and altering initial multiplication. The two mechanisms lead to a complex dislocation network that boosts strain hardening. A theoretical method is used to quantify the effect of the process. The contribution proportions of grain boundaries, dislocations, amorphous atoms, and solid solutions are 53.9 %, 24.2 %, 16.0 %, and 5.9 %, respectively. Furthermore, excessive incident energy is found to cause intergranular brittle fracture during tension, primarily due to the oversized grain size and significant differential slip. Additionally, the amorphous proportion significantly affects the wear volume. This research represents an innovative study in ion implantation/nitriding, significantly contributing to the advancement of hybrid processes.