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© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

It has been reported that the duplex bainite microstructure obtained by austempering (AT) shows higher strength, ductility and impact toughness than quench and tempered (QT) martensite structure in SAE9254 spring steel. However, there seems to be no research on the very high cycle fatigue (VHCF) and tribology characteristics of bainite structure for durability design of next generation spring steel from the perspective of engineering and industrial applications. This is a follow-up study that quantitatively analyzed the mechanical properties, microstructural deformation characteristics, and impact toughness of bainite and martensite using EBSD (Electron Backscatter Diffraction) and SEM (Scanning Electron Microscope) analyses. In this study, VHCF, HCF, tribology characteristics and UNSM (ultrasonic nanocrystal surface modification) effects under duplex bainite and single martensite microstructures were quantitatively studied and analyzed by fracture mechanics from the engineering and industrial point of view to improve durability and weight reduction in spring steels. The bainite AT and martensite QT specimens showed a 56% and 33% increase in fatigue limit for as received AR specimens. Fisheye cracks in duplex bainite AT specimens are similar to ‘facet internal cracks’ that initiated in the absence of inclusions. Generally fisheye crack fracture mode is preferred in VHCF, but fisheye crack was not found in the QT and the AR specimens at all. The UNSM-treated specimens showed fatigue limits that were about 33~50% higher than the untreated specimens.

Details

Title
VHCF, Tribology Characteristics and UNSM Effects of Bainite and Martensite Spring Steels
Author
Suh, Min Soo 1 ; Nahm, Seung Hoon 2   VIAFID ORCID Logo  ; Chang Min Suh 3   VIAFID ORCID Logo  ; Pyun, Young Sik 4 

 Korea Institute of Energy Research, Daejeon 34129, Korea; [email protected] 
 Korea Research Institute of Standards and Science, Daejeon 34113, Korea; [email protected] 
 School of Mechanical Engineering, Kyungpook National University, Daegu 41566, Korea 
 Department of Fusion Science and Technology, Sun Moon University, Asan 31460, Korea 
First page
901
Publication year
2022
Publication date
2022
Publisher
MDPI AG
e-ISSN
20754701
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2679780146
Copyright
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.