Abstract
During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool–chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI) 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD) method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM) was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear.
Highlights
Austenitic stainless steels are widely used in chemical industries and nuclear power industries because they have a good combination of high mechanical strength and corrosion resistance
A built-up edge (BUE) consists of highly deformed material layers, which are bonded to the tool surface and can lead to change the tool geometry and the mechanics of the process [5]
The main objective of this study is to investigate the close link between the BUE formation process and the surface integrity when machining austenitic stainless steel AISI 304
Summary
Austenitic stainless steels are widely used in chemical industries and nuclear power industries because they have a good combination of high mechanical strength and corrosion resistance. Austenitic stainless steels are considered difficult-to-machine materials because of their low thermal conductivity and high strain. Materials 2017, 10, 1230 hardening rate during cutting [3]. Their low thermal conductivity leads to heat concentration in the cutting zone that results in high localized temperatures. Their high work hardening leads to high adhesion of the workpiece material to the cutting tool, resulting unstable chip and built-up edge (BUE) formation [4]. BUE is not permanently situated on the cutting edge, but periodically becomes detached, sometimes adhering to the machined surface, and sometimes to the chip [6]. A thin and stable BUE can be used to protect the tool from wear by reducing the friction between the cutting tool and workpiece [7]
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