Tribological characterization of Al6061/alumina/graphite/redmud hybrid composite for brake rotor application

ABSTRACT

Dry sliding tribological characterization of redmud particle-reinforced Al6061/alumina/graphite hybrid metal matrix composite (RM-AlHMMC) was investigated as per ASTM G99-05 using pin on disc experimental setup. Initially, hybrid composites were fabricated through stir casting process by varying the wt.% of redmud particle as 3, 7, and 11, and then the wear tests were carried out based on L₂₇ orthogonal array. The experimental results revealed that 11 wt.% RM-AlHMMC showed maximum of 90% improved wear resistance than AlHMMC. For all the composites, the coefficient of friction (CoF) increases and saturates with the applied load and sliding distance, in which 11 wt.% RM-AlHMMC showed maximum of 48% increased CoF than AlHMMC. Metallographic investigation of worn-out AlHMMC composite showed that at maximum applied load, sliding velocity, and sliding distance, the wear mechanism changes from abrasive to adhesive, but adding of redmud particle showed combined adhesive and abrasive wear mechanisms. The optimized tribological parameters were obtained using grey relational analysis which revealed that 11 wt.% RM-AlHMMC has improved tribological properties.

KEYWORDS:

• Aluminum hybrid composites
• dry sliding wear
• grey relational analysis
• redmud particle

Abbreviations::

• Al6061-T6 alloy: aluminum T6 heat-treated alloy
• AlHMMC: aluminum hybrid metal matrix composite
• RM-AlHMMC: redmud reinforced AlHMMC
• HRB: Rockwell hardness B-scale
• OA: orthogonal array
• SWR: specific wear rate (mm³/Nm)
• CoF: coefficient of friction (µ)
• GRA: grey relational analysis
• GRC: grey relational coefficient
• GRG: grey relational grade