Evaluation of seizure resistance of bronze bearing alloys
Kortelainen, Fanny (2024)
2024
Master's Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2024-12-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-2024120810846
https://urn.fi/URN:NBN:fi:tuni-2024120810846
Tiivistelmä
Lead (Pb) is a common element in bronze bearing alloys due to its excellent anti-friction and anti-wear properties. Despite its benefits, Pb is nevertheless a harmful substance to health and the environment. There are many limitations regarding the use of Pb. In the future, more restrictions can be expected and even a full ban on Pb use is possible in the EU. There is a need to develop alternative, more sustainable Pb-free bronze bearing alloys to replace the widely used leaded tin (Sn) bronze.
The goal of industrial companies is to replace leaded Sn bronze with a more sustainable Pb-free bronze alloy in their bearing applications. The replacement bronze alloy must exhibit similar properties as leaded Sn bronze including good seizure resistance. The objective of this thesis is to evaluate the seizure resistance of four different bronze bearing alloys. Three commercially available bearing bronzes Sn bronze, leaded Sn bronze and aluminum (Al) bronze were tested in addition to a newly developed Pb-free bismuth (Bi) bronze. A new journal bearing device was designed to conduct an experiment in both hydrodynamic and boundary lubrication regimes to investigate seizure resistance. The seizure resistance was experimentally tested at constant oil flow and sliding velocity with stepwise applied normal load increase until the seizure occurred.
Pb-free Bi bronze showed potential to replace leaded Sn bronze in bearing applications. Pb-free Bi bronze behaved similarly to leaded Sn bronze in the mixed/boundary lubrication regimes in terms of transition load, temperature increase and coefficient of friction (CoF). Both leaded Sn bronze and Pb-free Bi bronze exhibited similar solid lubricant properties, as both were smeared onto the counterpart surface.
The goal of industrial companies is to replace leaded Sn bronze with a more sustainable Pb-free bronze alloy in their bearing applications. The replacement bronze alloy must exhibit similar properties as leaded Sn bronze including good seizure resistance. The objective of this thesis is to evaluate the seizure resistance of four different bronze bearing alloys. Three commercially available bearing bronzes Sn bronze, leaded Sn bronze and aluminum (Al) bronze were tested in addition to a newly developed Pb-free bismuth (Bi) bronze. A new journal bearing device was designed to conduct an experiment in both hydrodynamic and boundary lubrication regimes to investigate seizure resistance. The seizure resistance was experimentally tested at constant oil flow and sliding velocity with stepwise applied normal load increase until the seizure occurred.
Pb-free Bi bronze showed potential to replace leaded Sn bronze in bearing applications. Pb-free Bi bronze behaved similarly to leaded Sn bronze in the mixed/boundary lubrication regimes in terms of transition load, temperature increase and coefficient of friction (CoF). Both leaded Sn bronze and Pb-free Bi bronze exhibited similar solid lubricant properties, as both were smeared onto the counterpart surface.