Cutting performance of cubic boron nitride-coated tools in dry turning of hardened ductile iron

A novel cubic boron nitride (cBN)-coated silicon nitride(Si₃N₄) cutting tool was fabricated via the diamond interlayers by electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (MPCVD) technique. The cutting performance of cBN-coated tools was evaluated by dry turning of hardened ductile iron in comparison with the commercially available titanium aluminum nitride (TiAlN)-coated tools. The effects of cutting parameters on the cutting force and cutting temperature were studied. The results showed that the cutting forces increased with the increase of depth of cut but decreased with the increase of cutting speed, while the cutting temperature increased with the increase of cutting speed. Compared to the TiAlN-coated tools under identical turning conditions, the cBN-coated tools had lower cutting force and cutting temperature, and smaller tool wear. The cBN-coated tools delivered excellent cutting performance and prolonged tool life. Furthermore, the wear patterns and wear mechanisms of cBN-coated tools were investigated. It was found that the dominant wear patterns were crater wear on rake face and flank wear land, and the wear mechanisms were demonstrated to be abrasion wear and diffusion wear. The cutting experiments verified that the cBN-coated tools had attractive potentials in the applications for dry turning of refractory metals and hardened ferrous materials.