Influence of grit blasting treatment using steel slag balls on the subsurface microhardness, surface characteristics and chemical composition of medical grade 316L stainless steel

Slag is a residue from the steel making processes which is at present still considered as an industrial waste due to its low utility. In this paper, the spherical steel slag balls obtained from the slag atomization process are evaluated for use in grit blasting treatment of medical grade 316L stainless steel. The modification in subsurface microhardness, surface characteristics (morphology, roughness, mass loss) and chemical composition of the stainless steel after the grit blasting treatment with these particles is examined. The blasting treatment was carried out for 5–20 min using steel slag balls with a size of 1–2 mm in diameter and 0.7 MPa compressed air flow in normal direction toward the surface of the specimen. The result shows the increasing subsurface microhardness, surface irregularity and roughness of the stainless steel by this treatment. Surface material removal takes place as well during the blasting treatment as indicated by the mass loss of the specimen. The mechanisms of the subsurface microhardness modification as well as those for the surface roughness and mass loss evolution during the grit blasting treatment are elucidated in this paper. The blasting treatment with the steel slag balls also introduces some bioactive elements such as Ca, Si and Mg on the specimen surface. In conclusion, the grit blasting treatment using the steel slag balls has potential for improving mechanical properties and bioactivity of stainless steel based biomedical implants.