Invited presentation:
Abrasive wear performance of quenched wear resistant steels – effects of composition and microstructure Niko Ojala1)*, Kati Valtonen1), Marke Kallio2), Joonas Aaltonen2), Pekka Siitonen2) and Veli-Tapani Kuokkala1) 1) Tampere
University of Technology, Department of Materials Science, Tampere Wear Center, Finland 2) Metso Minerals, Inc., Finland *email:
[email protected]
Originally presented and published 8th – 13th September 2013, Torino, Italy
“Effects of composition and microstructure on the abrasive wear performance of quenched wear resistant steels”, Wear 317(2014)225-232
FIMECC DEMAPP PROGRAM
Motivation • Quenched wear resistant steels are widely used in industrial applications. • The Brinell hardness grades are considered as standards. • But the wear performance is not extensively studied.
Overview to topics 1) Materials and methods
2) Results
3) Discussion FIMECC DEMAPP PROGRAM
15 commercially available 400 HB steels were tested • Sheet thicknesses were 10 or 12 mm. • Decarburization layers were removed before testing 0.250
1000 900 800
0.150
600 500
0.100
0.176
0.180
0.186
0.189
0.192
0.199
0.202
0.208
0.216
E
0.173
D
0.172
C
0.165
B 0.163
A 0.158
0.050
400
0.142
Mass loss [g]
700
0
2
15
4
14
3
10
11
5
24
18
17
6
16
1
0.000
300
200 100
Surface hardness [HV5]
0.200
0
• Five steels were selected to closer study. FIMECC DEMAPP PROGRAM
Crushing pin-on-disk • •
The equipment is based on the pin-on-disk principle In the tests, the pin is repeatedly pressed against the gravel bed and the disk with a pneumatic cylinder – The pin does not come into direct contact with the disk at any time
•
The loss of material of both the pin and the disk are measured by weighting, and the size change of the abrasive during the test can measure by sieving
Test parameters • Disk speed: 20 rpm • Disk material: S355 (200 HV) • Pin pressure: 1.1 bar – 235 N nominal crushing force
• Pretest: 15 minutes, 10 minutes contact time – 500 grams of 2/4 mm granite
• Test: 30 minutes, 20 minutes contact time – With granite gravel according to the table
800
140%
700
120%
600
100%
500
80%
430
450 390
350
60%
400
300 153%
135%
131%
200 116%
40% 20%
400
0%
100
Surface hardness [HV5]
160%
100%
Mass loss compared to steel A
Up to 50 % difference in abrasion wear performance
0 A
B
C
D
E FIMECC DEMAPP PROGRAM
Tempered martensite with untempered white martensite C
A
E
B
D
20 µm
High-stress abrasive wear Wear mechanism dominated by two-body abrasion (Soft disc, hard pin) A
E
High-stress abrasive wear Scratches, tearing, deformations, lip formation…
Differences in wear surface deformations
A
B
C
E
Differences in wear surface deformations Steel C Granite-steel tribolayer Sharp interface Lack of deformation/orientation Steel B Embedded granite particle Orientation Deformations No sharp interface
Chemical compositions and microstructure • Hardenability – Carbon – Molybdenum (+Nickel) – Boron
• Martensite formation – Total amount of alloying elements – Amount of aluminum and nickel
S teel
A
B
C
E
Chemical composition (wt%) C
0.16
0.15
0.15
0.14
Si
0.4
0.28
0.22
0.38
Cr
0.14
0.37
0.41
0.46
Ni
0.04
0.07
0.09
0.04
Mo
0.15
0.1
0.01
0
Al
0.034
0.031
0.1
0.025
N
0.005
0.006
0.005
0.007
B
0.003
0.001
0.002
0.002
∑
2.349
2.013
2.4
2.519
Steel D is removed due to probable manufacturing faults
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Deformations and work hardening • Deformation depths up to 60 µm • The best wear performance was achieved by steels having good orientation of the deformed surface layer – Steels A and B: thick deformation layers with smooth orientation
• The highest initial hardness and also highest local work hardening did not result as best performance – Hardest layers in steel C 820 HV0.05 vs. 605 HV0.05 in steel B
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Concluding remarks • Marked differences between the commercial 400 HB grade quenched steels in the wear performance • Wear process: two-body abrasive cutting • Hardenability and auto-temperability are required for good initial properties • Deformations and work hardening are natural ‘defense mechanisms’ for steels – but over hardening leads to brittle like behavior and increased wear losses
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Niko Ojala Research Scientist, Doctoral student Tampere University of Technology Department of Materials Science, Tampere Wear Center P.O.Box 589, FI-33101 Tampere, Finland phone: +358 50 317 4516 email:
[email protected] www.tut.fi/twc/en
