Microhardness and tribological behavior of a glass-ceramic produced from a glass in the MgO-CaO-SiO_2-P_2O_5-F system have beer investigated with regard to the phases formed and microstructure developed during crystallization. The results of X-ray diffraction analysis indicatec that apatite and wollastonite are the predominant crystalline phases. Scanning electron microscopy examination revealed that the wollastonite crystal content decreases and apatite crystal content increases as the depth distance from the surface increases. Structure oriented changes in properties were evidenced. The indentation microhardness at the free surface was 650 + - 12 Hv. However, it decreased gradually with increasing depth distance frorr. the free surface and attained 520 + - 8 Hvat a distance of0.5 mm below the free surface. The wear rate at the free surface was 0.7 + - 0.05 x 10~(-4)mm~3/Nm, but increased gradually as the distance from the free surface increased. The wear rate reached 2.9 + - 0.15 x 10~(-4) mm~3/Nm at a distance of 0.5 mrr below the free surface.
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