Few studies dedicated to the service life of thrust bearings have mostly focused on surface wear, without investigating subsurface microstructural changes or establishing any correlation between these evolutions and the underlying wear mechanisms. This study investigates wear mechanisms and microstructural changes in grease-lubricated thrust ball bearings under false brinelling. Perfluorinated grease degradation increases friction and shear, promoting adhesive and oxidative wear. KAM and EBSD analyses reveal plastic deformation localized in martensite, with fragmentation. To enable a finer analysis of subsurface damage, techniques such as TEM and SAED analyses show nanostructuring of martensite near the surface and carbide-matrix interactions without decohesion. Inter-carbide spacing measurements and TEM cross-sections confirm carbide clustering in high shear zones. Reorientation of carbides under false brinelling stresses favors crack propagation. Partial carbide dissolution, identified via TEM, leads to iron and carbon diffusion into the martensite, increasing hardness and brittleness. This promotes crack initiation, flaking, and debris formation, which intensify local stresses. These results highlight the interplay between lubrication efficiency, microstructural evolution, and damage mechanisms.