Influence of B/ZrO2 molar ratios on the ambient temperature wear properties of composites made by an Al-ZrO2-B system

The dry sliding wear characteristics of the composites fabricated by an Al-ZrO2-B system were investigated by using a pin-on-disc wear tester at ambient temperature. With the increase of sliding velocity, the wear rates increase to the highest values at 0.8 m/s and then decrease. When the molar ratio of B/ZrO2 is 0, the reinforcements are composed of Al3Zr blocks and α-Al2O3 particles. The wear resistance of the composites is not satisfactory due to the low strength and brittleness of the Al3Zr phase. With an increase in the molar ratio of B/ZrO2, the wear properties of the composites are significantly improved due to the decrease of Al3Zr blocks and the increase of ZrB2 particles. When the B/ZrO2 molar ratio increases to 2, the Al3Zr blocks almost disappear and the α-Al2O3 and ZrB2 are the reinforcements of the composites, which make the composites exhibit good wear resistance. With the increase of the B/ZrO2 molar ratios, the values of friction coefficients decrease slightly, while their varied ranges decrease remarkably and the friction of the composites becomes more stable.