Fig. 2

SEM and OM images of the surface layer and cross-sections of the inscribed plaque: a 600 × SEM secondary electron image of the surface layer. b 124 × SEM backscatter image of the cross-sections. c 200 × OM image of the cross-sections)

SEM and OM images of the surface layer and cross-sections of the inscribed plaque: a 600 × SEM secondary electron image of the surface layer. b 124 × SEM backscatter image of the cross-sections. c 200 × OM image of the cross-sections)