A descriptive phenomenological model for white layer formation in hard turning of AISI 52100 bearing steel. (January 2021)

• Record Type: Journal Article
• Authors: Hosseini, S.B.; Klement, U.
• Is Part Of: CIRP journal of manufacturing science and technology. Volume 32(2021)
• Page Start: 299
• Page End: 310
• Publication Date: 2021-01
• Subjects: WL White layer -- DL Dark layer -- T-WL Thermally induced white layer -- M-WL Mechanically induced white layer -- LOM Light optical microscopy -- SEM Scanning electron microscopy -- TEM Transmission electron microscopy -- XRD X-ray diffraction -- GIXRD Grazing Incidence X-ray diffraction -- APT Atom probe tomography -- Vc Cutting speed [m/min] -- VB Tool flank wear [mm] -- ap Depth of cut [mm] -- f Feed [mm/rev] -- Ff Feed force [N] -- Fc Cutting force [N] -- Fp Passive force [N] -- HRC Hardness Rockwell C -- TTA Time-Temperature-Austenitisation -- Ms Martensite start temperature -- Mf Martensite finish temperature -- Ac1 Critical temperature when entering α + γ + carbide region -- Ac3 Critical temperature when entering γ + carbide region -- Acc Critical temperature when entering ɣ region -- t Duration of contact [μs] between the tool and workpiece surface -- T˙ Heating rate [°C/s] -- T¨ Cooling rate [°C/s]; White layer -- Dark layer -- Hard-Turning -- Phase transformation -- Severe plastic deformation; Manufacturing processes -- Periodicals; 670.5
• DOI: 10.1016/j.cirpj.2021.01.014
• Languages: English
• ISSNs: 1755-5817

Abstract

Abstract: This paper investigates the characteristics and the formation of white layers and dark layers induced by hard turning of through-hardened AISI 52, 100 steel. The investigation showed that different types of white layers exist e.g., formed predominantly through excessive thermal or mechanical energy loading. The thermally induced white layer is formed when the cutting temperature is above the critical austenitisation temperature for the material. The nano-sized microstructure is initiated through dynamic recovery, which transitions to dynamic recrystallisation when the temperature rises above the onset temperature for dynamic recrystallisation. The corresponding white layer is characterised by a higher retained austenite content compared to the unaffected material, and the presence of a dark layer beneath the white layer. The white layer and the adjacent dark layer are found to be ∼12% harder and 14% softer, respectively, compared to the unaffected material. On the other hand, the mechanically induced white layer is formed through severe plastic deformation, where the formation is controlled by dynamic recovery and results in an elongated and broken-down substructure. Neither austenite nor an adjacent dark layer could be found for such white layers. The mechanically induced white layer is ∼26% harder than the unaffected material. For both types of white layer, (Fe, Cr)3 C carbides are found in the microstructure. The investigation shows that the heating rate, cooling rate, pressure, and duration of contact between the cutting tool and workpiece surface should also be considered to understand the underlying formation mechanisms. The characteristics of the examined white layers and the cutting conditions are summarised in a descriptive phenomenological model in order to create a systematic approach for the definition of the different types of white layers.