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The role of retained austenite in dry rolling/sliding wear of nanostructured carbide-free bainitic steels
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.ORCID-id: 0000-0003-1162-4671
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.ORCID-id: 0000-0002-9100-7982
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.ORCID-id: 0000-0003-1454-1118
2019 (engelsk)Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 428-429, s. 193-204Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The dry rolling/sliding wear of nanostructured bainite has been investigated and compared with that of a conventional quenched and tempered bearing steel. In order to elucidate the role of retained austenite on the wear performance, high silicon hypereutectoid bearing steel with an identical alloy composition was heat treated to obtain different microstructures with similar hardness and different amounts of retained austenite. The results indicate that the nanostructured bainite can meet the minimum hardness requirements for bearing applications. Moreover, the nanostructured bainite outperformed the tempered martensitic steel in terms of wear resistance. The work hardening capacity and thus wear resistance increases due to the transformation of retained austenite into martensite. The results of XRD analyses show that the higher stability of retained austenite and strength of bainitic ferrite leads to better wear performance. It is demonstrated that the stability of retained austenite outweigh the influence of retained austenite content on wear resistance. Adhesion and oxidation were identified as the main wear mechanisms. In addition to microstructure, surface oxidation also plays a prominent role in determining the wear resistance. 

sted, utgiver, år, opplag, sider
Elsevier, 2019. Vol. 428-429, s. 193-204
Emneord [en]
Bearings, Carbide-free bainite, Nanostructured materials, Retained austenite, Rolling-sliding, TRIP effect
HSV kategori
Forskningsprogram
Maskinelement
Identifikatorer
URN: urn:nbn:se:ltu:diva-73366DOI: 10.1016/j.wear.2019.03.012ISI: 000471596300019Scopus ID: 2-s2.0-85063237323OAI: oai:DiVA.org:ltu-73366DiVA, id: diva2:1301083
Merknad

Validerad;2019;Nivå 2;2019-04-01 (svasva)

Tilgjengelig fra: 2019-04-01 Laget: 2019-04-01 Sist oppdatert: 2020-05-30bibliografisk kontrollert
Inngår i avhandling
1. On the role of microstructure in wear of nanostructured carbide-free bainitic steels
Åpne denne publikasjonen i ny fane eller vindu >>On the role of microstructure in wear of nanostructured carbide-free bainitic steels
2020 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The significance of steel production for the development of sustainable society and economy is immense. Today’s fast growing global economy poses an increasing demand for improving the properties of steel. The development of nanostructured carbide-free bainitic steel with an excellent combination of strength and toughness is an attempt to satisfy this global demand. During austempering, the precipitation of cementite can be suppressed by addition of approximately 1.5 wt% silicon and a duplex microstructure comprising of extremely fine aggregates of retained austenite and bainitic ferrite can be obtained. Owing to their excellent mechanical properties, these novel steels exhibit considerable potential to replace quenched and tempered bearing steel or pearlitic rail steel. In these applications, wear play a crucial role in determining the performance of the components. However, the majority of studies have been limited to mechanical properties of these steels but not much attention has been paid to their tribological behaviour. Notably, the role of retained austenite and bainitic ferrite on wear performance has not yet fully understood. Furthermore, machining process is an inevitable step in the manufacturing of metal products. During the machining, contact temperature can rise to several hundred degrees. However, high temperature tribological behaviour of these steels in conjunction with coated cutting tool has not yet been addressed. Therefore, the aim of the present research work is to gain a deeper understanding of the correlation between microstructure and tribological performance of carbide-free bainitic steels in various conditions.To achieve this aim, tribological behaviour of nanostructured carbide-free bainitic steels has been investigated under dry rolling/sliding, sliding and two-body abrasive wear conditions. A number of steel grades were austempered under a wide range of temperatures and durations to obtain different carbide-free bainitic microstructures. The results have been compared with that of quenched and tempered bearing steel. Moreover, high temperature tribological behaviour of carbide-free bainitic and 316L stainless steels during interaction with TiAlN PVD coating has also been studied under dry reciprocating sliding condition.The results show that a relatively higher retained austenite content and its stability enhance wear resistance under rolling/sliding condition. Moreover, wear performance of carbide-free bainitic steel has been found to be superior to that of the quenched and tempered bearing steel. However, under sliding condition, the effect of retained austenite on wear heavily depends on sliding speed. At low sliding speed and under adhesive-dominated wear condition, higher retained austenite content results in improved wear performance due to the higher work hardenability. In contrast, at high sliding speed where oxidative wear is dominant, a microstructure with the lowest content of retained austenite exhibits the highest wear resistance. The higher amount of bainitic ferrite provides a hard underlying substrate for a thin and mechanically stable compositional mixed layer and thereby enhances the wear resistance. The formation and microcracking of a brittle white etching layer of quenched and tempered steel is responsible for its inferior wear resistance. Under two-body abrasive wear conditions, higher retained austenite content leads to improved wear resistance. A microstructure providing an optimum combination of hardness and toughness shows the best abrasive wear resistance. During reciprocating sliding, the tribological response of carbide-free bainitic steel is altered with increasing temperature. Higher temperature results in severe material transfer from carbide-free bainitic steel to TiAlN coated cemented carbide. Furthermore, at elevatedtemperature, a porous oxide layer grows on the transferred materials and reduce friction coefficient.In summary, there is no simple and general relationship between microstructure and wear resistance. Depending upon the dominant wear mechanisms and operating conditions, retained austenite and bainitic ferrite affect the wear behaviour in radically different manners.

sted, utgiver, år, opplag, sider
Luleå: Luleå University of Technology, 2020
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Emneord
Tribology, Wear, Microstructure, Carbide-free bainite, Nanostructured, Retained austenite, Steel, High temperature
HSV kategori
Forskningsprogram
Maskinelement
Identifikatorer
urn:nbn:se:ltu:diva-79092 (URN)978-91-7790-613-1 (ISBN)978-91-7790-614-8 (ISBN)
Disputas
2020-10-06, E632, Luleå, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2020-06-01 Laget: 2020-05-30 Sist oppdatert: 2020-06-03bibliografisk kontrollert

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