Formation of lubricated tribo layer, grain boundary precipitates, and white spots on titanium-coated graphite–reinforced hybrid composites

Abstract

In this present investigation, AA7050 hybrid composite reinforced with boron carbide (B4Cp) and graphite (Gr) was fabricated through stir casting. The AA7050/B4Cp/Gr hybrid composites were prepared with 7.5 wt.% boron carbide particles added with 2.5, 5, 7.5 and 10 wt.% of graphite. Addition of potassium titanium fluoride (K2TiF6) flux improved the bonding of matrix and reinforcement due to the titanium interface. The influence of graphite particles on mechanical, wear, sulphide stress corrosion cracking and electric discharge machining was analysed. A new wear equation for graphite-reinforced composites based on transient wear equation and Archard’s equation was derived. The hardness, tensile strength and wear resistance of hybrid composites reduce with increase in graphite weight percentage. The graphite-reinforced hybrid composites showed improvement in sulphide stress corrosion cracking due to grain boundary precipitates. The material removal rate of hybrid composites increases with increase in graphite weight percentage, and it exhibits poor surface finish due to poor heat dissipation.