{"title":"Microstructural and elemental analysis of flow lips of heavy haul curved rails affected by deformation driven phase transformation","authors":"Sudharm Rathore , Soumyajit Mojumder , Cong Qiu , Peter Mutton , Aparna Singh","doi":"10.1016/j.wear.2024.205462","DOIUrl":null,"url":null,"abstract":"<div><p>A combination of optical imaging (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) was used to examine the white etching layer (WEL) and brown etching layer (BEL) formed in the flow lip region of a heavy haul curved rail. These flow lips eventually serve as crack initiating regions, leading to reverse detail fractures. OM distinctly identified the WEL/BEL region based on light contrast, while SEM micrographs identified a fine-grained structure within the WEL with intermittent patches of a deformed pearlitic structure. SEM images of the WEL/BEL indicate that the fraction of cementite patches was higher in the BEL region than in the WEL. TEM investigations revealed the presence of martensite/nano-crystalline ferrite along with newly formed austenite and cementite particles in the WEL and the BEL. The ferrite/martensite grain size was much finer in the WEL than in the BEL. The lath morphology of martensite was observed in the BEL, whereas a mixed morphology of lath and twinned martensite was observed in the WEL. APT studies show no Mn/Si partitioning in WEL/BEL along with C-concentrations ranging from 10 to 15 at.% and up to 20 at.% in the WEL and BEL respectively. The synergistic effect of elevated wheel-rail contact temperatures and severe plastic deformation dictated the overall microstructural evolution of the BELs and WELs on the outer rail surface in the flow lip.</p></div>","PeriodicalId":23970,"journal":{"name":"Wear","volume":null,"pages":null},"PeriodicalIF":5.3000,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Wear","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0043164824002278","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
引用次数: 0
Abstract
A combination of optical imaging (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) was used to examine the white etching layer (WEL) and brown etching layer (BEL) formed in the flow lip region of a heavy haul curved rail. These flow lips eventually serve as crack initiating regions, leading to reverse detail fractures. OM distinctly identified the WEL/BEL region based on light contrast, while SEM micrographs identified a fine-grained structure within the WEL with intermittent patches of a deformed pearlitic structure. SEM images of the WEL/BEL indicate that the fraction of cementite patches was higher in the BEL region than in the WEL. TEM investigations revealed the presence of martensite/nano-crystalline ferrite along with newly formed austenite and cementite particles in the WEL and the BEL. The ferrite/martensite grain size was much finer in the WEL than in the BEL. The lath morphology of martensite was observed in the BEL, whereas a mixed morphology of lath and twinned martensite was observed in the WEL. APT studies show no Mn/Si partitioning in WEL/BEL along with C-concentrations ranging from 10 to 15 at.% and up to 20 at.% in the WEL and BEL respectively. The synergistic effect of elevated wheel-rail contact temperatures and severe plastic deformation dictated the overall microstructural evolution of the BELs and WELs on the outer rail surface in the flow lip.
期刊介绍:
Wear journal is dedicated to the advancement of basic and applied knowledge concerning the nature of wear of materials. Broadly, topics of interest range from development of fundamental understanding of the mechanisms of wear to innovative solutions to practical engineering problems. Authors of experimental studies are expected to comment on the repeatability of the data, and whenever possible, conduct multiple measurements under similar testing conditions. Further, Wear embraces the highest standards of professional ethics, and the detection of matching content, either in written or graphical form, from other publications by the current authors or by others, may result in rejection.