Abstract
White structure flaking (WSF) has been found to be one of the failure modes in bearing steels under rolling contacts through the formation of cracks associated with a microstructural change called white etching area (WEA). In the present research, the effects of the high-pressure torsion (HPT) process on the microstructure and mechanical properties of an AISI 52100 alloy are studied. An annealed AISI 52100 was subjected to high-pressure torsion at room temperature under a pressure of up to ~6 GPa for up to three turns. Finite-element modeling (FEM) was used to simulate the process under high-pressure torsion and quasi-constrained conditions to reveal the material property changes occurring in HPT. Scanning electron microscopy and microhardness testing after processing were used to investigate the microstructural and mechanical property evolution of the steel. Strain induced microstructural transformations occur and affect the mechanical properties in a similar way to the well-known white etching area (WEA) found beneath the surface of wind turbine bearings. Here, HPT is used to study the feasibility of creating microstructural changes that are similar to WEA. This paper presents the preliminary results of using HPT to produce WEAs.
Highlights
Bearing steels have been widely used for over 100 years in various applications
Standard rollers of AISI 52100 bearing steel were used in this study and the chemical composition and mechanical properties of the roller material are shown in Tables 1 and 2, respectively
Results of the Effective Strain in High Pressure Torsion (HPT) Discs element simulations showed thatinplastic deformation occurred in a steady-state way
Summary
White structure flaking (WSF) is a damage mechanism responsible for a large amount of failures of bearings in wind turbine gearboxes [1]. WSF is related to microstructural changes registered close to the contact zones called white etching areas (WEAs) [2]. WEAs in AISI 52100 consist of carbon saturated nanograins of ferrite, which vary in sizes in the 10–100 nm range [3]. It has been suggested that WEAs form in a region of localized high plastic deformation, as a consequence of the presence of a high dislocation density, low temperature recrystallization and high carbon dissolution from the cementite into the ferritic matrix. WEAs are found to be associated with micro cracks (White Etching Cracks or WECs). The nature and relationships between WEA and micro-cracks are not completely understood [4]
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