Abstract
The main objective of this paper is to clarify the formation mechanism of built-up layer (BUL) in cutting of hardened steel, as BUL formed on the tool surface under certain cutting conditions can act as a protective layer, increase the tool wear resistance, extend the tool life and so on. Detailed analyses of tool surface, the microstructure feature of BUL and chip inside surface after cutting hardened steel S45C (H-S45C) were done by Scanning Electron Microscope (SEM). Experimental evidences show that the formation of BUL is a process of the nucleus formation on the tool rake face. Furthermore, a nucleus formation mechanism of BUL formation mechanism is proposed. The model is based on a qualitative and quantitative analytical approach including an atomic-scale contact model at the tool/ chip interface and a nucleus formation of BUL from irreversible thermodynamics point of view. A quantitative comparison between model and experimental results is also provided. It is verified that simulation results are in good agreement with the experimental results and the model is able to predict the position of the nucleus formation of BUL. This study may help researchers deepen the understanding of the formation mechanism of BUL and clarify some previous concepts on it.
