Crystallographic preferred orientation induced by cyclic rolling contact loading
- PDF / 1,809,997 Bytes
- 21 Pages / 612 x 792 pts (letter) Page_size
- 13 Downloads / 223 Views
I.
INTRODUCTION
BALL and roller bearings experience local changes in the microstructure when exposed to high rolling contact stresses. These alterations, including, for example, changes in the amount of retained austenite and the development of residual stress, have been observed applying optical microscopy,[1] transmission electron microscopy,[2,3] and X-ray diffraction.[4,5] Also, texture (crystallographic preferred orientation) may develop, in association with microstructural changes, from accumulated subsurface plastic deformation.[6,7] In general, deformation textures become noticeable in conjunction with a significant change in shape of the deformed workpiece. However, as will be shown here, such macroscopic shape changes are absent in the event of subsurface texture formation. In this article, results of experimental texture analysis for the ferrite matrix and of material-displacement analysis are presented. These analyses were performed in the dark etching region (DER) of fatigue tested 6309 type deep groove ball bearing inner rings (Figures 1 and 2); the dark appearance after etching is indicative of the microstructural changes.[1] Texture has been characterized using X-ray diffraction methods. The material displacement has been measured using a specially developed autoradiographic labeling method.[8] The texture development will be discussed in relation to other changes in the microstructure of the specimen. The alterations in retained austenite and residual stress have been discussed in References 4 and 5, respectively. The alterations in microstrain have been determined here from X-ray diffraction line broadening. The textures observed in the DER will be compared with the texture A.P. VOSKAMP, Senior Engineer, is with SKF Engineering & Research Centre B.V., 3430 DT Nieuwegein, The Netherlands. E.J. MITTEMEIJER, Professor, is with the Laboratory of Materials Science, Delft University of Technology, 2628 AL Delft, The Netherlands. Manuscript submitted November 16, 1995. METALLURGICAL AND MATERIALS TRANSACTIONS A
development for three other basic types of loading: (a) rolling, (b) cyclic push-pull, and (c) cyclic reversed torsion. II.
EXPERIMENTAL
A. Material The 6309 type (Figure 1) deep groove ball bearing inner rings investigated were manufactured from electroslag remelted SAE 52100 steel (high purity quality), subjected to a standard heat treatment (austenitizing 860 7C for 15 minutes; quenched in oil at 60 7C; and tempered for 1 hour at 150 7C) producing predominantly a tempered martensitic structure, 10 to 15 vol pct retained austenite, and about 3 to 5 vol pct globular cementite, corresponding with a hardness of 850 HV30. B. Rolling Contact Fatigue Testing For this study, 6309 type deep groove ball bearings, were tested under a purely radial bearing load. Inner rings used for texture and displacement analyses were available after testing at different combinations of load, rotational velocity, running temperature (measured at the flange of the outer ring), and number of stress cycles applied. In
Data Loading...
