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Application oriented wear
testing of wear resistant steels
in mining industry
Niko Ojala
Doctoral student
Tampere Wear Center
Tampere University of Technology
Tampere, FINLAND
High Tech Steel Conference
NSCAS 2016
15.8.2016
Motivation
• Demanding abrasive erosion conditions have
not been studied extensively (erosion by
large particles)
In mining applications:
• The speeds of the particles
can be up to 30 m/s
(pumps)
• The size of the particles
can vary from micrometers
to several centimeters
Motivation
• Change in wear environment/mechanisms
(e.g. from low-stress to high-stress wear)
requires new material solutions and research
Shear band
Low- vs. high-stress
slurry erosion
Contents
• Application oriented wear testing
– What? Why?
• Is it possible to simulate industrial wear
processes in laboratory?
– The wear testers
• Mechanical behavior of the steels in abrasive
wear conditions
• Summary
Application oriented wear
testing
• Laboratory testing where the focus is on
simulating industrial applications
– real conditions, real wear phenomena,
real wear losses
• In short:
Why application oriented?
• Vast amount of wear related publications
have been done over last 40-50 years
• Simplified consensus is:
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.
400
500
600
700
800
900
0 50 100
Hard
nes
s [H
V]
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
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
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
Publication:Ojala et al. “Effects of composition and microstructure
on the abrasive wear performance of quenched wear
resistant steels”,
Wear 317 (2014) 225–232
Crushing pin-on-disk tester
Mechanical behavior of the steels
in high-stress wear conditions
Two commercial steels from same hardness grade, but two
totally different mechanical behavior on wear surfaces in
dry high-stress abrasion. [Wear 317 (2014) 225–232]
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
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.[Wear, 354-355 (2016) 21-31]
• Strain hardening is a natural defense mechanism of
crystalline materials
• But it may lead to less ductile behavior on wear surface[Wear 354-355 (2016) 21-31]
Summary
• Application oriented wear testing have proved to
offer added value to simulating demanding
applications in laboratory scale
• Without correct material response it is impossible
to have good correlation with laboratory tests
– Low- vs. high-stress conditions
– Hardness alone doesn’t dictate the wear
performance of quenched wear resistant steels in
demanding conditions (like mining)
– Ductile to brittle transition on wear surfaces
observed in high-stress wear
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]
twitter: @Ojala_NJT
www.tut.fi/twc/en
