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Research Papers: Friction and Wear

Tribological Characterization of AZ91 and AE42 Magnesium Alloys in Fretting Contact

[+] Author and Article Information
D. Khabale

Tribology Laboratory,
Mechanical Engineering Department,
National Institute of Technology Srinagar,
Hazratbal,
Srinagar 190006, Jammu and Kashmir, India

M. F. Wani

Tribology Laboratory,
Mechanical Engineering Department,
National Institute of Technology Srinagar,
Hazratbal,
Srinagar 190006, Jammu and Kashmir, India
e-mail: mfwani@nitsri.net

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 21, 2017; final manuscript received May 6, 2017; published online July 21, 2017. Assoc. Editor: Dae-Eun Kim.

J. Tribol 140(1), 011604 (Jul 21, 2017) (21 pages) Paper No: TRIB-17-1028; doi: 10.1115/1.4036922 History: Received January 21, 2017; Revised May 06, 2017

Fretting wear studies were conducted on AZ91 and AE42 magnesium alloys against steel ball. Average coefficient of friction (COF) remains steady with the increase in running time. However, average coefficient of friction decreases with the increase in normal load and frequency and marginally increases with the increase in amplitude. A constant average coefficient of friction of 0.06 was observed for both AZ91 and AE42 under dry sliding conditions at normal load of 50 N. Wear volume increases linearly with increasing running time. Wear volume first decreases sharply, attains minima, and then increases marginally with the increase in normal load. However, wear volume increases with increasing amplitude and frequency. Higher specific wear rate of 10.5 × 10−6 mm3 N−1·m−1 was observed for AE42, as compared to 4.5 × 10−6 mm3 N−1·m−1 for AZ91. The wear in magnesium alloy was caused by a combination of adhesion, abrasion, oxidation, delamination, and plastic deformation under different fretting conditions.

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Figures

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Fig. 1

Optical micrograph of wear track of disk

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Fig. 2

(a) Universal tribometer with fretting test setup. (b) Schematic of fretting wear test setup: (1)—disk sample, (2)—clamp for disk sample, (3)—ball specimen, (4)—ball holder, (5)—electromagnetic reciprocating drive, (6)—load actuator, (7)—arm, (8)—piezoelectric sensor, and (9)—supporting frame.

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Fig. 3

Optical micrographs of (a) AZ91 and (b) AE42 as cast magnesium alloys

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Fig. 4

(a) SEM micrograph of AE42, (b) EDS of four different points: (c) point 1, (d) point 2, (e) point 3, and (f) point 4

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Fig. 5

HV versus indentation load/dwell time: (a) AZ91 (indentation load), (b) AE42 (indentation load), (c) AZ91 (dwell time), and (d) AE42 (dwell time)

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Fig. 6

Indent image of AZ91 alloy at different indentation load: (a) 20 g, (b) 50 g, (c) 100 g, and (d) 200 g for 10 s dwell time

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Fig. 10

Average coefficient of friction (μ) versus frequency (Hz)

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Fig. 7

Average coefficient of friction (μ) versus running time

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Fig. 8

Average coefficient of friction (μ) versus normal load (N)

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Fig. 9

Average coefficient of friction (μ) versus fretting amplitude (μm)

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Fig. 11

Wear volume (mm3) versus running time

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Fig. 12

Wear volume (mm3) versus normal load (N)

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Fig. 13

Wear volume (mm3) versus fretting amplitude (μm)

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Fig. 14

Wear volume (mm3) versus frequency (Hz)

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Fig. 15

Specific wear rate for AZ91, AE42, and steel ball

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Fig. 16

SEM micrographs of alloy wear tracks after 10 h fretting test: (a) AZ91 disk, (b) AE42 disk, (c) steel ball of AZ91, and (d) steel ball of AE42

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Fig. 17

(a) EDS spectrum of different points on AZ91 disk wear track after 10 h of fretting test and (b) EDS spectrum of different points on counterface steel ball wear track against AZ91 after 10 h fretting test

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Fig. 18

Friction plot and hysteresis loops for AZ91 magnesium alloy obtained at normal loads: (a) 5 N, (b) 50 N, and (c) 150 N

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Fig. 19

Wear track of AZ91 at 5 N normal load: (a) optical micrograph, (b) SEM micrograph, and (c) EDS spectrum

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Fig. 20

(a) Optical micrograph, (b) SEM micrograph, and (c) its EDS spectrum for AZ91 at 150 N normal load

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Fig. 21

Three-dimensional profilometry image and surface texture for AZ91 wear tracks at different loads: (a) 5 N, (b) 50 N, and (c) 150 N

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Fig. 22

(a) Optical micrograph, (b) SEM micrograph, and (c) its EDS spectrum for AZ91 at 125 μm amplitude

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Fig. 23

Optical micrographs and SEM micrographs of AE42 wear track under 5 Hz frequency: (a) optical of AE42 disk, (b) SEM of AE 42 disk, (c) optical micrograph of counterface steel ball, and (d) SEM of counterface steel ball

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Fig. 24

EDS of counterface steel ball wear track against AE42 under 5 Hz frequency

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Fig. 25

Optical micrographs and SEM of AE42 wear track under 60 Hz frequency: (a) optical AE42 disk, (b) SEM of AE 42 disk, (c) optical of counterface steel ball, and (d) SEM of counterface steel ball

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Fig. 26

(a) EDS spectrum of different points on AE42 disk wear track under 60 Hz frequency and (b) EDS spectrum of different points on counterface steel ball wear track against AE42 under 60 Hz frequency

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Fig. 27

Three-dimensional profilometery image and surface texture of AE42 alloy wear track under different frequency: (a) 5 Hz and (b) 60 Hz

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