Surface Finishing Mechanisms of cBN Burnishing Tool Composed of Fine BN Grains for Hardened Die Steel

• Published in: International journal of automation technology Vol. 19; no. 5; pp. 970 - 979
• Main Authors: Nakata Koki, Okada Masato, Watanabe Hidehito, Watanabe Masahide
• Format: Journal Article
• Language: English
• Published: Tokyo Fuji Technology Press Co. Ltd 01.09.2025
• Subjects: Ball burnishing; Burnishing; Compressive properties; Cubic boron nitride; Die steels; End milling; Feed direction; Inclination angle; Morphology; Polycrystalline diamond; Residual stress; Sliding; Surface finish; Surface finishing; Surface layers; Surface roughness
• ISSN: 1881-7629; 1883-8022
• DOI: 10.20965/ijat.2025.p0970

Sliding burnishing process is a high-value-added finishing process that smooths the surface, hardens the surface layer, and adds compressive residual stress by sliding a hard tool across the target surface. It contributes to automation and improves quality in the die and mold polishing process. In this study, the mechanisms underlying surface finish generation by a cubic boron nitride (cBN) ball burnishing tool with a smooth tool surface composed of fine BN grains were clarified in comparison with a polycrystalline diamond (PCD) ball end mill, which generates a surface finish via a grinding effect. Additionally, the impact of tool posture and tool feed direction of the cBN ball burnishing tool relative to the target surface on the material flow morphology of the surface layer of the finished surface was analyzed. At the same tool pressing force, the depth of the processing marks obtained with the cBN ball burnishing tool was shallower than that obtained with the PCD ball end mill, and the compositional distribution of the surface material was less distinct than in the PCD one. Even with such a difference in the surface finish generation mechanisms, the surface roughness and residual stress of the surface finish obtained with the cBN ball burnishing tool were almost the same as those of the PCD ball end mill, indicating good surface finish quality. For the cBN ball burnishing tool, differences were observed in the flow morphology of the surface layer of the finished surface depending on the tool inclination angle to the target surface and the tool feed direction. By considering these effects of tool posture and tool feed direction, it was experimentally proven that surface roughness less below \mathitRa=10 nm and high compressive residual stress can be achieved.