Study on microstructure, mechanical and tribological properties of a novel high-entropy alloy based self-lubricating composite Al_0.5CrFeNiV_0.5-hBN

A new high-entropy alloy (HEA) based self-lubricating composite with good mechanical and tribological properties has been designed and fabricated, using Al_0.5CrFeNiV_0.5 HEA as matrix and hexagonal boron nitride (hBN) as solid lubricant. In addition to the well dispersed hBN particles, the novel composite is consisted of (Al,Ni)-rich, (Cr,V)-rich, (Cr,Fe,V)-rich, CrVB₄, and AlN phases. High temperature nanoindentation tests of the composite revealed its excellent thermal softening resistance, showing very good mechanical strength stability in a wide temperature range. Additionally, the composite also exhibits substantial improvements in friction reduction and anti-wear performance from RT to 700 °C. The enhanced mechanical and tribological properties are attributed to the hBN and new phases formed by reactions between hBN and Al_0.5CrFeNiV_0.5 HEA matrix. The main wear mechanisms during sliding of the Al_0.5CrFeNiV_0.5-hNB composite against the Si₃N₄ balls shift from abrasion and plastic deformation to oxidation and adhesive wear as the wear testing temperature is increased.