The effects of boriding parameters on kinetics, microstructure, and corrosion behavior of Ramor 500 and Ramor 550 steels were investigated. Despite their wide use in defense, there is a lack of scientific data on the surface modification of Ramor armor steels. While other steels are well-known, the boron diffusion and bilayer formation in these specific alloys are not yet fully understood. This makes it difficult to predict how boriding affects their performance in harsh conditions. Our study fills this gap by providing a precise kinetic dataset, which allows for regression-based modeling to optimize the boriding process for better durability. The steels were borided at 900 °C, 950 °C, and 1000 °C for 2, 4, and 6 h using pack boriding with Ekabor II powder. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the microstructure and elemental composition of boride layers. X-ray diffraction (XRD) analysis revealed the presence of FeB and Fe2B phases in the boride layers. A bilayer boride structure, consisting of an outer FeB layer and inner Fe2B layer, was observed in all borided samples. The boride layer thickness increased with boriding temperature and time, following a parabolic growth law. Activation energies for boron diffusion were calculated as 120.54 kJmol-1 and 126.21 kJmol-1 for Ramor 500 and Ramor 550 steels, respectively. Microhardness measurements showed a gradual decrease from surface to substrate, with maximum values between 1800 and 2000 HV. Electrochemical tests in 3% NaCl solution demonstrated that boriding improved corrosion resistance by forming a dense boride barrier, with no significant differences between the steels. The study provides quantitative insights into optimizing boriding parameters by achieving activation energies of 120.54–126.21 kJmol-1 surface hardness up to 2000 HV, and improved corrosion resistance in 3% NaCl solution for Ramor 500 and Ramor 550 steels widely used in military and industrial applications.
Hasan Onur Tan (Thu,) studied this question.