Structural, mechanical and tribological properties of Cu–ZrO2/GNPs hybrid nanocomposites

Hybrid Cu–ZrO2/GNPs nanocomposites were successfully produced using powder metallurgy technique. The effect of GNPs mass fraction, 0, 0.5, 1 and 1.5%, on mechanical and tribological properties of the produced hybrid nanocomposite was studied while maintaining ZrO2 mass fraction constant at 5%. High energy ball milling was applied for mixing powders and compaction and sintering were applied for consolidation. The morphological analysis of the produced powder showed acceleration of Cu particles fracture during ball milling with the addition of GNPs up to 0.5% with noticeable reduction of agglomeration size. Moreover, the crystallite size of Cu–5%ZrO2/0.5%GNPs hybrid nanocomposites revealed smaller crystallite size, 142 nm, compared to 300 nm for Cu–5%ZrO2 nanocomposite. Additionally, the hybrid nanocomposite with 0.5% GNPs shows homogeneous distribution of both reinforcement phases in the sintered samples. This improved nano and micro structure of Cu–5%ZrO2/0.5%GNPs nanocomposites revealed higher hardness, 169.3 HV, compared to 65.5 HV for Cu–5%ZrO2 nanocomposite. The wear rate is decreased in this composite while it increased with increasing GNPs content more than 0.5%. The coefficient of friction is decreased as well for this hybrid nanocomposite and remain constant with increasing GNPs content more than 0.5%.