Materials, Methods & Technologies, Volume 18, 2024

Rezumat: AISI 304L stainless steel is an austenitic steel with general uses. However, its chemical composition and mechanical properties are relatively similar to those of AISI 316L. The main difference between the two steels is probably the molybdenum content in AISI 316L, which makes it more apt to face corrosion. This study evaluates the possibility of offering AISI 304L as an alternative to the demand for materials resistant to corrosion in biomedical applications by improving its chemical and mechanical surface properties. First, samples of AISI 304L were thermochemically treated with a thermochemical hardening process known as boriding to generate a hard surface layer of iron borides, the FeB/Fe2B type, on the steel samples. The boriding process has been demonstrated to be effective in protecting the surface of treated materials against wear and corrosion, even in chloride-rich environments. The thermochemical powder-pack boriding process was performed at a constant temperature of 950 °C for 2, 4, and 6h. The effect of the hard layers on the cellular viability of human fetal osteoblast (HFOb) cells was evaluated using a resazurin reduction (CellTiter Blue) assay. After 2, 4, and 6h of exposure to the treatments, layers of FeB/Fe2B with 12.30, 23.60, and 30.65 µm thicknesses were obtained, respectively. The hardness of the layers ranged from 1992.40 to 2397.54 HV (at least ten times higher than that of the non-treated steel). The viability results suggest that the samples exposed to boriding exhibited better cellular proliferation than the non-treated AISI 304L steel. These results open the possibility of generating materials with better capability to face corrosion and wear conditions in biological environments.