PSI - Issue 75

10

D. Jbily et al. / Procedia Structural Integrity 75 (2025) 158–175 Author name / Structural Integrity Procedia (2025)

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Fig. 12 presents a Kernel Average Misorientation (KAM) map of the subsurface microstructure near the tooth surface in worn areas. In comparison to non-worn areas (Fig. 11 Erreur ! Source du renvoi introuvable. ), the shot peened (SP) specimen exhibits a marked decrease in grain misorientation at the surface within the worn zone, whereas no misorientation was observed for the REF specimen, as in the non-worn area. This decrease in misorientation is likely attributable, on one hand, to material removal due to wear to a depth of approximately 40 µm, and on the other hand, to residual stress relaxation induced by friction.

REF Pinion

SP Pinion

Unindexed zone at the extreme surface

Fig. 12. KAM map (Kernel Average Misorientation) of the teeth in the worn zones.

No grain misorientation was observed at the extreme surface in either case after testing. However, a significant loss of indexing was detected in this region, suggesting that severe work hardening may have occurred. This loss of crystallographic information indicates that the material in these zones has likely evolved into an amorphous state, preventing the generation of diffraction signals.