Effect of dynamic recrystallization at tool-chip interface on accelerating tool wear during high-speed cutting of AISI1045 steel

Acceleration of tool crater wear in high-speed cutting is usually attributed to the high tool-chip interface temperature increasing diffusion coefficient(D-Eff), where the role of microstructure is ignored. The main purpose of this paper is to study the influence of microstructure evolution at second shear zone on tool element diffusion ability and crater wear with increasing cutting speed, which establishes the base for the research of tool wear evolution forecast. Based on the Orthogonal turning experiment of AISI1045 steel, the effect of cutting speed(V) on crater wear and microstructure of second shear zone was notable: (I) the crater wear increased drastically at 361 m min(-1) < V < 560 m min(-1), in which the change to lower or higher cutting speed was relatively flat; (2)the images obtained by field-emission scanning electron microscopy showed dramatically microstructure evolution occurred at second shear zone, and extremely refined dynamic recrystallization grain, with 80 nm to 300 nm grain size, was formed as cutting speed increased. The very fine dynamic recrystallization grain significantly increased the fraction of high-diffusion channel (grain boundary area), and thus the diffusion coefficient was enhanced. Based on this idea, the impact of dynamic recrystallization grain, coupled with tool-chip interface temperature calculated by Oxley model, on diffusion coefficient was explored by Hart equation. The analysis has shown that the influence of dynamic recrystallization grain on tool crater wear was significant by increasing D-Eff. (C) 2015 Elsevier Ltd. All rights reserved.