Investigation of multiple machinability parameters in the drilling of AISI 316L stainless steel materials

AISI 316L stainless steel is widely used in industries such as aerospace, healthcare, biomedical devices, and food processing. However, due to its low machinability characteristics, cutting processes face challenges, leading to the formation of poor-quality hole surfaces. In this context, the primary aim of this study is to investigate the effects of increased surface hardness and microstructure, achieved through different burnishing processes applied prior to drilling, on properties such as burr formation, cutting forces, and surface roughness for this steel, which is also widely used in the orthopedic implant sector. In this study, burnishing processes with 2 and 3 passes were first performed using a Chromium Carbonitride (CrCN) coated sintered carbide spherical tool to improve surface quality. Then, blind holes of 30 mm depth were drilled with a coated HSS drill bit (9.8 mm diameter) using different drilling methods. The results showed that the burnishing process increased the material's microhardness values and hardness depth. It was also observed that the drilling method and burnishing conditions influenced the cutting forces. The lowest Fz values were obtained under the fixed-step reaming method with the samples subjected to 2-pass burnishing. Additionally, as hardness increased, burr width, burr root width, and burr height decreased. Furthermore, the burnishing process improved the surface roughness values of the hole inner surfaces, with the best results achieved under the 2-pass burnishing conditions.