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Technical Brief

Effects of Process Parameters on White Layer Formation and Morphology in Hard Turning of AISI52100 Steel

[+] Author and Article Information
Xiao-Ming Zhang

State Key Laboratory of Digital Manufacturing
Equipment and Technology,
Huazhong University of Science and Technology,
Wuhan 430074, China;
Fachgebiet Strukturdynamik,
Technische Universität Darmstadt,
Darmstadt 64287, Germany
e-mail: zhangxm@sdy.tu-darmstadt.de

Li Chen, Han Ding

State Key Laboratory of Digital Manufacturing
Equipment and Technology,
Huazhong University of Science and Technology,
Wuhan 430074, China

1Corresponding author.

Manuscript received September 13, 2015; final manuscript received February 5, 2016; published online March 9, 2016. Assoc. Editor: Guillaume Fromentin.

J. Manuf. Sci. Eng 138(7), 074502 (Mar 09, 2016) (9 pages) Paper No: MANU-15-1475; doi: 10.1115/1.4032769 History: Received September 13, 2015; Revised February 05, 2016

Hard turning is becoming increasingly considered by industry as a potential substitute for grinding. However, it is greatly hurdled by surface integrity problems such as tensile residual stress and white layer, which are generally found to have negative effects on the stress corrosion, wear resistance, and fatigue life of the machined parts. This paper investigates white layer formation and morphology in hard turning process using various process parameters, taking into account the effects of heat treatment which results in microstructure and hardness differences on bulk materials. Samples undergone three typical heat treatment processes are prepared and then machined using different cutting speeds and radial feed rates. Optical microscope, scanning electron microscope (SEM), and X-ray diffraction (XRD) are employed to analyze the microstructures of white layer and bulk materials after varies heat treatments and cutting processes. Through the studies, we find the existence of a cutting speed threshold, below which no white layer forms for both the low and medium-temperature tempering. The threshold value increases; however, the white layer thickness decreases under the same cutting conditions, for the low and medium-temperature tempering, respectively. Also, we find that the white layer thickness and the scattering of it along the cutting direction on the surface increases with cutting speed and radial feed rate. White layer with wavy morphology can be found in samples after quenching at high cutting speed. We first discover that the pitch of the white layer with wavy morphology is similar to the displacement of tool at the time a segment of the serrated chips forms. Also, the surface residual stresses of the samples are measured. Relationship between white layer and residual stresses is presented. Based on the relationship we reveal that high temperature is more dominant than volume expansion for white layer formation.

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References

Figures

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Fig. 4

The cutting edge geometry

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Fig. 5

Variation of white layer thickness values and the standard deviations with (a) cutting speed under the three heat treatments and (b) radial feed rate under heat treatment I

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Fig. 6

Micrographs at the cut-in end, the middle, and the cut-out end of the sample generated at 155 m/min, heat treatment I

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Fig. 7

Boundary and initial conditions of Eulerian-based A.L.E model

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Fig. 8

Strain and temperature of nodes in the vicinity of the tool tip for test No. 5

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Fig. 9

Variation of depth of cut and white layer formation at the cut-in end

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Fig. 10

White layer with wavy morphology and serrated chip formation

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Fig. 11

Cutting force in hard turning when radial feed rate is 0.1 mm (Fy is the radial cutting force, and Fz is the tangential cutting force)

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Fig. 12

SEM images of white layer generated at 0.1 mm/r and (a) 155 m/min, heat treatment I, (b) 116 m/min, heat treatment II, and (c) 232 m/min, heat treatment III

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Fig. 13

Diffractograms taken on specimen No. 8

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Fig. 3

Metallographic figures for workpieces undergone different heat treatments before cutting. (a) Spheroidizing annealing only, (b) heat treatment I, (c) heat treatment II, and (d) heat treatment III.

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Fig. 2

Heat treatment processes for the workpieces

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Fig. 1

Experimental test setup

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Fig. 14

Diffractograms taken on specimen No. 14

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Fig. 15

Diffractograms taken on specimen No. 20

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Fig. 16

Retained austenite content of base materials and surfaces with white layer for three different heat treatments (cutting speed is 345 m/min)

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Fig. 17

Variation of surface residual stresses with (a) cutting speed under the three heat treatments and (b) radical feed rate under heat treatment I

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