Wear performance of quenched wear resistant steels in abrasive slurry ...

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Aug 15, 2016 - An application oriented approach for mining applications: • Sample speeds 5 – 20 m/s. • Abrasive particles up to 10 mm size. – Natural gravels ...
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 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? Field test compared to application oriented dry-pot and conventional (sandpaper) abrasion tests.

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

900

CFB270 Dry-pot

CFB270 Field

CFB300 Dry-pot

CFB300 Field

Zero work hardening in abrasion test !!

Hardness [HV]

800 700 600

500

Dry-pot

Field

Abrasion test

Similar 400 material response in dry-pot and field

0

50 Distance [µm]

100

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

Crushing pin-on-disk tester

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

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]

Two steels with same wear tester, two different abrasives, two different wear environments: Low- vs high-stress conditions -> two different material responses 400HB steel

500HB steel

8/10 mm granite, 80 minutes

Shear band

0.1/0.6 mm quartz, 80 minutes

Ojala et al. ”Edge effect in high speed slurry erosion wear tests of steels and elastomers”, NORDTRIB 2016, June 2016, Finland.

• 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]

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]

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