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.