Sliding wear tests and numerical modelling of Co- and Fe- based alloys
File(s)
Author(s)
Bastola, Ajit
Type
Thesis
Abstract
Cobalt-based alloys have excellent wear and corrosion resistance, making them desirable for tribological applications in the nuclear industry. However, they can cause high background radiation dose levels from the activation of cobalt-containing wear and corrosion products. A combined experimental and modelling approach was used to understand and quantify surface modifications in bearing surfaces for nuclear applications.
The present study compared the wear performance of two new Fe-based alloys, recently developed by Rolls-Royce plc, with other Co- and Fe-based alloys. In the first test group, Group 1, the sliding wear of two newly developed alloys, DS A1 and DS A2, is analysed. The second test group, Group 2, compares the sliding wear performance of DS A1 alloy against 440C martensitic steel. Group 3 entails benchmark sliding tests for Co-based alloys. The last group, Group 4, compares the performance of RR2450 ball wear against Haynes 25 counterface. The counterface pairs of Group 1 and Group 2 outperform in wear resistance compared to the other groups. Wear mass losses were highest for Group 3 alloys, followed by Group 4 alloys. Oxidation improved the wear resistance of Fe-based alloys. Thick ($>$1 \si{\micro\metre}) oxide layers on surfaces of Fe-based alloys provided significant protection, while thinner, poorly adhering oxides on Co-based alloys offered minimal benefit.
The study also presents a validated finite element method for simulating wear profiles in both continuous and reciprocating sliding scenarios. The wear simulation procedure is based on Archard’s wear equation using the UMESHMOTION subroutine available in a commercial FE package, ABAQUS. The developed methods are appropriate for general 3D deformable-deformable solid elements. The method is applicable to a wide range of sliding wear tests and can be updated to consider tribofilm or oxide layer growth or removal for both 2D and 3D surfaces.
The present study compared the wear performance of two new Fe-based alloys, recently developed by Rolls-Royce plc, with other Co- and Fe-based alloys. In the first test group, Group 1, the sliding wear of two newly developed alloys, DS A1 and DS A2, is analysed. The second test group, Group 2, compares the sliding wear performance of DS A1 alloy against 440C martensitic steel. Group 3 entails benchmark sliding tests for Co-based alloys. The last group, Group 4, compares the performance of RR2450 ball wear against Haynes 25 counterface. The counterface pairs of Group 1 and Group 2 outperform in wear resistance compared to the other groups. Wear mass losses were highest for Group 3 alloys, followed by Group 4 alloys. Oxidation improved the wear resistance of Fe-based alloys. Thick ($>$1 \si{\micro\metre}) oxide layers on surfaces of Fe-based alloys provided significant protection, while thinner, poorly adhering oxides on Co-based alloys offered minimal benefit.
The study also presents a validated finite element method for simulating wear profiles in both continuous and reciprocating sliding scenarios. The wear simulation procedure is based on Archard’s wear equation using the UMESHMOTION subroutine available in a commercial FE package, ABAQUS. The developed methods are appropriate for general 3D deformable-deformable solid elements. The method is applicable to a wide range of sliding wear tests and can be updated to consider tribofilm or oxide layer growth or removal for both 2D and 3D surfaces.
Version
Open Access
Date Issued
2023-03-17
Date Awarded
01/02/2024
License URL
Advisor
Dini, Daniele
Stewart, David
Sponsor
Engineering and Physical Sciences Research Council
Rolls-Royce PLC (Firm)
Grant Number
EP/L015900/1
EP/N025954/1
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)