Effect of Hexagonal Boron Nitride Addition on the Cutting Performance of the Laser Modified Zone of Vermicular Graphite

Laser surface technology could significantly increase the wear resistance and hardness of materials; nevertheless, laser-modified zone must be reprocessed to meet the functional and assembly requirements. However, differences in the hardness, microstructure, and tribology of the modified zone lead to severe tool wear damage. This study investigated the impact of adding hexagonal boron nitride (h-BN) powder on the cutting performance of cladding layers to reduce the wear of cutting tools. The h-BN modified zone was prepared on vermicular graphite cast iron. The microstructure and microhardness of the modified zone were also investigated. Conducted milling experiments on the modified zone at different cutting speeds and effects of h-BN on cutting force, machined surface roughness and tool wear were studied. The results revealed that the microstructure of the modified zone was primarily consisted of tree structures and columnar. The microhardness of the modified zone is much higher than that of the matrix, and the addition of h-BN has not influence the hardness of the modified zone obviously. The machined surface roughness and main cutting force of the h-BN samples were lower than those of the h-BN–free samples at the same cutting speed. An analysis of the tool failure mechanism revealed that chipping, spalling, and oxidation wear constituted the main wear mechanisms of the tool rake face during cutting process of the two samples. Adding h-BN did not change the wear mechanism of the cutting tool but could effectively reduce the degree of tool wear. In addition, the tool flank of the cutting h-BN samples had a lower wear bandwidth and boundary wear.