IMPROVING THE TOOL LIFE OF CUBIC BORON NITRIDE TOOLS IN MACHINING HIGH-STRENGTH CAST IRONS

Abstract

The study focuses on improving the wear resistance of polycrystalline cubic boron nitride (PCBN) cutting tools during the turning of high‑strength cast irons, including compacted graphite iron (CGI), spheroidal graphite iron (SGI) and austempered ductile iron (ADI). Based on the analysis of peer‑reviewed publications, it is shown that the reduction of tool life in machining these materials is governed by the combined influence of their microstructure—namely graphite morphology and matrix phases—the mechanics of chip formation, and the thermal conditions in the cutting zone. Continuous chip flow and crater wear dominate in CGI, adhesion‑controlled “build‑up and break‑off” cycles prevail in SGI, while ADI demonstrates a pronounced abrasive contribution due to its bainitic matrix [1,3,4,7].Typical PCBN wear patterns, including crater formation on the rake face and flank wear (VB), were evaluated together with their dependence on cutting parameters, cutting‑edge geometry (rake‑face chamfer, honing radius) and cooling strategy. It is shown that chamfering and edge honing reduce stress concentration and suppress micro‑chipping, whereas avoiding intermittent changes between dry and lubricated conditions prevents thermal shock [3,5,12].Practical recommendations are formulated, including moderate cutting speeds and feeds to stabilize heat flow, strengthened edge geometry for interrupted cutting or machining of ADI, and appropriate criteria for tool life based on VB and crater‑to‑edge remaining cross‑section. Integrated optimization of tool geometry, cutting parameters and thermal conditions increases PCBN tool life by a factor of 1.5–4 while maintaining surface integrity [3,6,7].The article extends current understanding of PCBN behaviour in high‑strength cast iron machining by systematically linking microstructural features with dominant wear mechanisms and by providing experimentally grounded guidelines for improving process reliability and tool longevity.