Cutting Performance and Wear Mechanism of Coated Silicon Nitride Cutting Tool in Turning of High Hardness Alloy Steel

Silicon nitride cutting tool, which is widely applied to machine cast irons, is not suitable for steel cutting because of the massive chemical wear between silicon nitride and ferrous materials. Covering protective coating (s) on tool surface is an effective way to isolate the chemical contact between cutting tool and workpiece. The aim of this paper is to investigate the cutting performance and cutting mechanism of coated silicon nitride cutting tools on steel machining. The cutting performances of uncoated and CVD-Al2O3/TiN coated silicon nitride cutting tool when cutting high hardness alloy steel AISI 4340 under dry condition were investigated. Studies include tool flank wear, tribological behavior of the tool-chip interface and wear mechanisms for both uncoated and coated silicon nitride cutting tools. The results showed that the tool life of silicon nitride cutting tools can be improved to a great extent with the cover of CVD-Al2O3/TiN coating by avoiding crater failure and reducing friction during steel cutting.