Figure 5. Representative scanning electron microscopy (SEM) photographs of the materials after 40,000 two-body wear cycles (×40 magnification).

(A) Group 1; (B) Group 2; (C) Group 3; (D) Group 4; (E) Group 5; (F) Group 6; (G) Group 7; (H) Group 8; (I) Group 9 (A), (B) and (C), large indentation produced by localized wear was observed on each specimen.; (D), (E) and (F), the size of the indentations was small, but their outline was unclear; (G), (H) and (I), the specimens showed indistinct indentations