Last and latest presentation about my PhD thesis before it will be published in start of year 2017. You can follow the work at https://www.researchgate.net/project/Doctoral-thesis-Application-oriented-wear-testing-of-wear-resistant-steels-in-mining-industry

1. Application oriented wear
testing of wear resistant steels
in mining industry
Niko Ojala
Doctoral student
Tampere Wear Center
Tampere University of Technology
Tampere, FINLAND
8th TWC International Wear Seminar
November 8th, 2016
Tampere, Finland

2. Motivation
• Demanding abrasive erosion conditions have
not been studied extensively (erosive/abrasive
wear by large particles)
In mining applications:
• The speeds of the particles
can be up to 30 m/s
• The size of the particles
can vary from micrometers
to several centimeters

4. Motivation
• Change in wear environment/mechanisms
(e.g. from low-stress to high-stress wear)
requires new material solutions and research
Low- vs. high-stress
slurry erosion

5. Contents
• Application oriented wear testing – What? Why?
• Is it possible to simulate industrial wear processes
in laboratory?
• The wear testers
• Replicating wear of mining applications
• Material response in low- and high-stress wear
• Effect of abrasive embedment
• Summary

6. Application oriented wear
testing
• Laboratory testing where the focus is on
simulating industrial applications
– real conditions, real wear phenomena,
real wear losses
• In short:

7. Why application oriented?
• Vast amount of wear related publications
have been done over last 40-50 years
• Consensus is:

8. Is there need?
• An internet query for 42 companies, globally,
was performed
• Response rate was 62%
• About 60% reported a need for wear testing
that would better correlate with real
applicationsResults will be published in the thesis

9. Is it possible?
Publication:
Vuorinen, Ojala, et al., “Erosive and abrasive wear performance of
carbide free bainitic steels – comparison of field and laboratory
experiments”, Tribology international 98 (2016) 108-115
Field test compared to application oriented dry-pot
and conventional (sandpaper) abrasion tests.

10. Field test
Application oriented test
Conventional test

11. 400
500
600
700
800
900
0 50 100
Hardness[HV]
Distance [µm]
CFB270 Dry-pot CFB270 Field
CFB300 Dry-pot CFB300 Field
Dry-pot
Field
Abrasion test
Zero work
hardening
in abrasion
test !!
Similar
material
response
in dry-pot
and field
Dry-pot
closer to
field results
in wear
losses

12. High speed slurry-pot wear
tester
An application oriented approach for
mining applications:
• Sample speeds 5 – 20 m/s
• Abrasive particles up to 10 mm size
– Natural gravels and ores !!
Ojala, et al., “Wear performance of
quenched wear resistant steels in
abrasive slurry erosion”, Wear, 354-
355 (2016) 21-31

13. Dry-pot wear tester
• Samples submerged in to a bed of
dry abrasives
• Particle sizes
up to 10 mm
• Speeds
5 – 20 m/s
Vuorinen, Ojala, et al.,
Tribology international
98 (2016) 108-115

14. Crushing pin-on-disk
Ojala et al.
“Effects of
composition and
microstructure on
the abrasive wear
performance of
quenched wear
resistant steels”,
Wear 317 (2014)
225–232

15. Replicating wear of mining
applications
• Reproducing the environment: testing
parameters and conditions
– Particle size and speed, Angle of incidence etc.
• Imitate the shape of the component: sample
shape and edge wear
– Component shape, Edge effect
• Wear mechanisms and deformations: stress
state and material response
– Low- or high-stress conditions
– Wear surface features and deformations

16. Role of real contact area?
3D profile of large granite
abrasive
Schematic presentations
of a real contact area of
two arbitrary surfaces
[Gagan Srivastava, Carnegie Mellon University]

17. Material response in low-
and high-stress wear (for steels)
• High-stress wear
– Embedment of abrasives
– Tribolayer and/or composite layer formation
– Deformations -> work hardening, white layers
– Role of corrosion decreasing
• Low-stress wear
– Minimal embedment and tribolayer formation
– Non-existent deformations
– Role of corrosion higher

18. Two similar commercial steels, but two totally different
mechanical behavior and wear performances in high-stress
abrasion. [Wear 317 (2014) 225–232]

19. Shear band
8/10 mm granite,
80 minutes
0.1/0.6 mm quartz,
80 minutes
400HB steel 500HB steel
Ojala et al. ”Edge effect in high speed slurry
erosion wear tests of steels and elastomers”,
NORDTRIB 2016, June 2016, Finland.
Two steels with same wear tester, two different abrasives, two
different wear environments: Low- vs high-stress conditions
-> two different material responses

20. Cross-section of a quenched steel sample tested with 8/10 mm granite
slurry at 45° sample angle.
A) SEM BSE image of the plastically deformed surface layer and
B) SEM SE image of a stepwise formed scratch that has cut through the
deformed surface layer.
• Strain hardening is a natural defense mechanism of
crystalline materials
• But it eventually leads to exhaustion of ductility on wear
surfaces
[Wear 317 (2014) 225–232 , Wear 354-355 (2016) 21-31]

21. Effect of abrasive
embedment
• Steels and elastomers
were compared in
both low- and high-
stress slurry erosion
• Embedment of
abrasives in
elastomers were
studied by X-ray
tomography
500 µm
[Wear, 354-355 (2016) 21-31]

22. Volume loss calculated
from mass loss [cm3]
Direct volume loss
measurement [cm3]
Difference
400HB 0.027 0.020 -27 %
NR 0.015 0.025 +66 %
[Submitted to Wear, September 2016]
Results will be published in the thesis and are submitted to the journal

23. Summary
• Application oriented wear testing have proved to
offer added value to simulating demanding mining
applications in laboratory scale
• Without correct material response it is impossible
to have good correlation in laboratory tests
– Low- vs. high-stress conditions
– Hardness alone doesn’t dictate the wear
performance of wear resistant steels in high-stress
conditions
– Exhaustion of ductility on wear surfaces observed
in high-stress wear

24. Future work
• More field testing -> improving the correlation
between laboratory and field tests
• Effect of abrasive embedment on wear
performance
– Formation mechanisms still unknown
• More profound understanding of effect of
steels‘ composition and microstructure on
wear performance

25. 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: niko.ojala@tut.fi
twitter: @Ojala_NJT
www.tut.fi/twc/en