Tuning of mechanical and structural properties of 20Â MC 5 steel using N ion implantation and subsequent annealing

In the present work, effect of 50 keV nitrogen ion implantation on the structure and mechanical properties of as-implanted and annealed 20 MC 5 steel samples is investigated. XRD measurements confirmed the formation of α−FeN phase. The crystallite size and stress of the nitride samples is found to increase with the ion fluence. The calculated value of crystallite size and stress is ∼29.21 nm and ∼9.826 × 108 Pa, respectively, for 1 × 1016 ions/cm2 implanted sample. An increase in crystallite size (∼31.26 nm) and phase transformation from FeN phase to Fe2-3N and Fe4N phase is observed on annealing at 500 °C for 2 h. Atomic force microscopy results show that surface roughness and particle size are increasing with ion fluence. Mechanical properties studied using Micro-Vicker hardness tester showed that hardness of the annealed sample increases initially with ions fluences (∼8.4 GPa at 1 × 1015 ions/cm2) and then it starts decreasing to ∼4.66 GPa when sample is exposed to an ion fluence of 1 × 1016, due to limited solubility of nitrogen in steel. Finally, we have performed simulations using TRIM software to investigate the impurity profile in the samples under the influence of 50 keV ions. Our results show that the ion implantation technique is very good tool for controlled modification of mechanical properties of 20 MC 5 steel, and it can be used in various applications such as crankshafts, gears, engines and machinery parts.