ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
It is well known that microstructural changes occur in a steel bearing, when the bearing isoperated under conditions involving high cyclic stresses. When combined with relatively hightemperatures, such microstructural changes result in the flaking of the bearing raceway. In this paper,microstructural changes that occurred during rolling contact fatigue were investigated, and therelationship between these changes and fatigue life are discussed in association with therecrystallization behavior of martensite. Conventional bearing steel SUJ2 (SAE52100) wassubjected to partial solution treatment at 1133K for 2.4ks followed by oil quenching. The quenchedmaterial with a martensitic structure was tempered at 443K for 7.2ks, and then subjected to rollingcontact fatigue testing. The testing was performed at temperatures ranging from 373K to 443Kand surface pressures of 4.6GPa or 5.5GPa. During testing at 373K, flaking occurred from thesurface of the raceway due to non-metallic inclusion and without any marked microstructuralchanges. On the other hand, in the case of testing at 403K or more, flaking occurs after obviousmicrostructural changes. Firstly, dark etching constituent (DEC) formed around the area ofmaximum shear stress, which was followed by the formation of white etching constituent (WEC)within the DEC at 80 and 30 degrees to the rolling direction. TEM observations showed the changefrom martensite lath to dislocation cell structure within the DEC, and also the existence of fineferrite grains of 20nm through 100nm within the WEC. Arrhenius plots for the fatigue life indicatedthat the activation energy of the fatigue process corresponded to that of carbon diffusion in bccferrite. These results suggest that rolling contact fatigue originated from the WEC is controlled bythe diffusion of carbon in the ferrite matrix
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/15/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.539-543.4255.pdf
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