The effects of cutting conditions on mixed ceramic and cubic boron nitride tool wear and on surface roughness during machining of X200Cr12 steel (60 HRC)

Abstract

Alumina-based mixed ceramic (CC650) and cubic boron nitride-based (CBN) (CBN7020) tools are becoming mostly preferred for machining under severe conditions. The aim of this study is to investigate the effect of cutting parameters on ceramic and CBN tool wear in the hard turning of X200Cr12 steel. The results indicate that the comparison span for both tool materials is limited to a speed of 180 m/min at which catastrophic ceramic cutting edge collapse took place. The tool life ratio rose from 4.37 to 17.14 when the cutting speed evolved from 90 to 180 m/min in favour of CBN, which resisted up to a cutting speed of 350 m/min. The feed rate effect on roughness (μm) is satisfactorily predicted by a power model deduced from experimental data and is compared with a theoretical model. A correlation between surface roughness and tool wear is proposed for the usual cutting speed ranges and for the two tested inserts respectively. The analysis also revealed that, under the allowable wear limit, the ceramic tool gave quality surfaces with higher roughness than the CBN tool. In conclusion, this work highlights the fact that 120 m/min is the optimal cutting speed value for machining X200Cr12 steel using CBN7020 while 60 m/min is the optimal cutting speed value for CC650 steel.