PSI - Issue 75

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

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that there is a higher indexing rate at the core compared to the subsurface. The contrast images yield an indexing rate of 85% at the core, while it is 65% for the subsurface. Differences in grain structure are also observed, with clearer parent grain boundaries (groups of small grains) and larger sizes at the core compared to the elongated martensitic laths and smaller sizes in the subsurface.

(a) Core (b) Surface Fig. 10. IPF map of a REF gear tooth in a non-contact area, in a cross-sectional plane perpendicular to the pinion axis; (a) Core, (b) surface Fig. 11 presents an example of the subsurface microstructure in a Kernel Average Misorientation (KAM) image near the tooth surface in non-contact areas. The color scale reflects the degree of local misorientation between neighboring grains, which is typically associated with plastic deformation. In the shot peened (SP) specimen, pronounced grain misorientations are observed at a depth of approximately 10 µm. In contrast, the reference specimen (REF) exhibits negligible or no detectable misorientation in the same area.

REF Pinion

SP Pinion

Fig. 11. KAM map (Kernel Average Misorientation) of the teeth in non-contact areas.