Créé le : 07/02/2013
N. Jouini, P. Revel, G. Thoquenne, M. Bigerelle - 01/11/2011 - RC Fatigue Design…
Traditionally, components of hardened steels, such as bearings, gears, shafts, and rails are finished by grinding process. High precision turning could be an attractive alternative, if it allows obtaining better surface integrity that would improve component life in rolling contact, knowing that furthermore it is a process more friendly environmental, comparatively to the grinding process. In this paper, machining experiments are carried out on rolling contact fatigue of AISI 52100 bearing steel (60-62 HRC), using cubic Boron Nitride (c-BN) cutting tools under dry condition and varying cutting parameters. The surface integrity is characterized by surface roughness measurements, subsurface microstructure observations and residual stresses evaluation. Fatigue life tests are performed on a twin-disk machine. The SEM observations of the transversal cross-section show the presence of very fine white layer (<1µm) on the top surface and thermal affected zone of 35 µm in the sub-surface. Experimental results suggest that the effect of surface roughness on RCF life is more significant than the effect of the level of compressive residual stresses. Indeed, RCF life decreases with the increase of the average roughness (Ra). The roller bearing components can attain 5.2 million cycles with Ra = 0.11 µm, and 0.32 million cycles with Ra = 0.25 µm. In comparisowith grinding processes, the bearing components attaint 1.2 million cycles with conventional grinding (Ra = 0.2 µm) and 3.2 million cycles with grinding followed honing (Ra = 0.05 µm). Therefore, the high precision hard turning allows improving the surface integrity and RCF life of the roller bearing components.
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Guillaume Thoquenne
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