Study On Friction And Wear Behaviour Of Squeeze-cast A356-SiCp Composites

Particle-reinforced aluminium matrix composites(PAMCs)have been identified for achieving high specific strength and stiffness,good electrical and thermal conductivity,superior wear resistance and low thermal expansion.They are widely used in aerospace,automotive,mechanical electronics and other manufacturing areas.The casting method has the advantages of high production efficiency and is suitable for large-scale industrial production.It is a very promising method for preparing PAMCs.Based on the application of PAMCs in wear-resisting components such as pistons and cylinder liners of automobile engines,the A356-SiCp composite castings with different particulate volume fractions and squeeze pressures were prepared by stirring and direct-squeeze casting methods.The friction and wear experiments of A356-SiCp and HT250 were carried out at conditions of different particulate fractions,squeeze pressures and load in reciprocating conditions.The experimental results including wear rate and friction coefficient were obtained.The wear morphology and mechanism at different conditions for the composites with as-cast state and T6 status were investigated.With the increase of particulate volume fraction,the wear rate gradually decreases,and the friction coefficient decreases first and then increases.When the volume fraction of particle is 5%,the wear morphology of composites is step-like shape,and the wear mechanism is dominated by peeling wear.When the volume fraction of particles is 10%,the wear profile is furrows and pits,and the wear mechanism is slight abrasive wear.When the volume fraction of particle is 15%,the wear morphology is mainly pits and the corresponding wear mechanism is abrasive wear.With the increase of squeeze pressure,the wear rate of composites gradually decreases,and the friction coefficient increases gradually.When the squeeze pressure is 0 MPa,the wear morphology of as-cast composites is furrows,and the wear mechanism is abrasive wear.The wear morphology of T6 treated composites is a step-like shape,of which the wear mechanism is peeling wear.When the squeeze pressure is 50 MPa and 75 MPa,the bonding strength between the particles and the matrix is improved,and the wear mechanism is slight abrasive wear.When the squeeze pressure is 100 MPa,the interface bonding between the matrix and the particles is quite good,and the SiC particles were broken.The wear debris layer on the surface of the material is ploughed,and the wear mechanism is slight abrasive wear.With the increase of load,the wear rate of composites gradually increases and the friction coefficient decreases gradually.The wear mechanism of composites gradually changes from abrasive wear to peeling wear.When the load is 25 N,the friction and wear behavior of the composite material is characterized as a combination of abrasive wear and peeling wear.