Process limitation of ultrasonic burnishing for commercially available martensitic stainless steel

Ultrasonic burnishing is attracting ever-greater interest as a surface finishing process. Although the popularity of this method in manufacturing industry remains limited, research is being conducted to explore both the detailed aspects and the limitations of this method. Tangential misalignment is one of most influential parameters in determining the mechanical properties induced by ultrasonic burnishing. This study investigates the effect of tangential misalignment on the ultrasonic burnishing of martensitic stainless steel (Stavax) and the surface integrity of the processed workpiece. Both negative and positive misalignments (from 0° to 5°) angles were tested. Macro hardness, instrumental micro hardness and surface roughnesses were measured. The results revealed that at higher tangential misalignment (>5° and along the negative side), ultrasonic burnishing cannot be performed for this material. It was found that with an increase in misalignment, hardness and surface roughness increased. Instrumental micro hardness measured from the burnished end, through the depth, revealed that hardness started decreasing from 60 µm towards the center of shaft. This indicates that beside ultrasonic burnishing has induced surface hardness, effect of hardness has been induced up to 60 µm. Considering the previous literature on ultrasonic burnishing, it appears that the potential of ultrasonic burnishing has some limitations depending on the material properties.