Tham khảo tài liệu 'tribology - lubricants and lubrication part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 52 Tribology - Lubricants and Lubrication segregation in severely deformed regions Gegner et al. 2009 which is assumed to be inducible by cyclic material loading in rolling contact see section . The overall quite uniformly appearing DER see Figures 17a and 18c is displayed at higher magnification in the LOM micrograph of Figure 19a. On the micrometer scale affected dark etching material evidently occurs locally preferred in zones of dense secondary cementite. As well as the spatial and size distribution of the precipitation hardening carbides microsegregations . C Cr influence the formation of the DER spots. Subsurface fatigue cracks usually advance in circumferential . overrolling direction parallel to the raceway tangent in the early stage of their propagation Lundberg Palmgren 1947 as exemplified in Figure 19b Voskamp 1996 . The aged matrix material of the dark etching region exhibits embrittlement see also section that is most pronounced around the depth of maximum orthogonal shear stress where the indicative X-ray diffraction line width is minimal and the microstructure reveals intense response to the damage sensitive preparative chemical etching process. Fig. 19. LOM micrographs of a a detail of the DER of Figure 17a and b typical subsurface fatigue crack propagation parallel to the raceway around the depth of maximum orthogonal shear stress in the etched radial microsection of the inner ring of a deep groove ball bearing In the upper subsurface RCF life range of the instability stage above the XRD L10 equivalent value . b B according to Figure 10 shear localization and dynamic recrystallization DRX induce 100 110 and 111 211 rolling textures that reflect the balance of plastic deformation and DRX Voskamp 1996 . Regular flat white etching bands WEB of elongated parallel carbide-free ferritic stripes of inclination angles pf of 20 to 32 to the raceway tangent in overrolling direction occur inside the DER Lindahl Osterlund 1982 Swahn et .
