Performance of nano/micro CBN particle coated tools in superfinish hard machining

A two-stage composite coating method has been developed for coating of nano/micro cubic boron nitride (CBN) particles on cutting tools. Since nano/micro CBN particle coated tools are more cost-effective than solid polycrystalline CBN (PCBN) tools, a comprehensive study on the coated tools is required. This paper studies the performance of these tools in superfinish hard machining. Specimens were machined by a solid PCBN tool and CBN particle coated tools with two different CBN particle size distributions: less than 0.5 and 2 μm. The specimen machined by a tool with small CBN particle coating (less than 0.5 μm) showed more compressive residual stresses and less thermal damage below the machined surface than other specimens. Furthermore, the specimen machined by a tool with small CBN particle showed less residual stress scatter than other specimens. The rolling contact fatigue life was predicted by using a rolling contact fatigue life model. The rolling contact fatigue life predictions indicate that the predicted life of the specimen machined by a tool with small CBN particle coating is longer than that of other specimens. The results thus indicate that a tool with small CBN particle coating provides better performance than other tools in superfinish hard machining.