Analysis and characterization of friction behaviour on AA7075/ZrB₂ composite under dry sliding condition

Abstract

The effect of ZrB2 particle reinforced with AA7075 on the friction behaviour of composite under dry sliding condition was investigated. Argon gas enhanced liquid metallurgy technique was used for the preparation of the composite with varying ZrB2 particles 5–15 wt% in the AA7075 alloy matrix. Microstructure, x-ray diffraction (XRD), hardness and dry sliding friction were conducted by varying applied load ranges from 20–80 N, sliding velocity from 0.8–2.0 m s−1 and a constant sliding distance of 3000 m. Optical Microscope (OM) images clearly show the distribution of ZrB2 particles in the host matrix. The hardness of the composites increased with increasing the reinforcement particles. XRD result of composite revealed the formation of MgZn2, Al7Cu2Fe, and AlZn Precipates. In dry sliding, the Coefficient of Friction (COF) showed a fluctuating tendency and a decrease with increasing ZrB2 particles. Worn surface of the composites analysed through SEM, and XRD. Surface undulations on the worn surface were analyized through 3D surface roughness. A reduction was seen in COF, this was due to the formation of oxide rich tribolayer on the worn surface. Worn surface hardness increased with increasing applied load due to plastic instability underneath the worn surface. At low load and sliding velocity and low wt% fraction of ZrB2 condition, the worn surface characterized as deep grooves and generated wear debris were equi-axed particles, whereas at a high load and sliding velocity and high wt% fraction of ZrB2 reinforced condition, breakage of tribolayer and generated wear debris were delaminated sheets.