Fonksiyonel Derecelendirilmiş Ti6Al4V/Grafit Kompozitlerin Tribolojik Davranışlarının İncelenmesi

5. International Üsküdar Scientific Research Congress, İstanbul, Türkiye, 22 - 23 Kasım 2025, ss.440-450, (Tam Metin Bildiri)

Conventional single-phase materials often exhibit insufficient thermo-mechanical stability and

surface durability under engineering conditions involving high temperature, friction, and

complex stress gradients. Functionally graded materials (FGMs) have emerged as advanced

engineering solutions, providing superior performance through the gradual variation of material

properties. In this study, graphite-reinforced functionally graded Ti6Al4V metal matrix

composites were fabricated using pressure-assisted sintering, and their microstructural,

mechanical, and tribological behaviors were comprehensively investigated. After homogeneous

mixing of the composite powder containing 10 wt.% graphite, a bilayer structure consisting of

an upper Ti6Al4V/graphite layer (1000 µm) and a lower 100% Ti6Al4V layer (3000 µm) was

produced. The processing parameters were fixed at 950 °C, 45 MPa, and 45 min under a vacuum

atmosphere of 10-4 mbar. Microstructural observations revealed uniform distribution of graphite

along the Ti6Al4V particle boundaries, accompanied by grain refinement across the upper,

transition, and lower layers. The graphite addition suppressed the β phase and promoted an α-

phase-dominant structure in the upper layer. Consequently, the hardness increased from 355 ±

4.2 HV0.5 in the lower layer to 407 ± 3.5 HV0.5 in the upper layer due to microstructural

refinement. Tribological tests demonstrated that graphite reduced the coefficient of friction by

approximately 50% confirming its effective solid-lubricant behavior. Overall graphite

reinforcement markedly enhanced the microstructural integrity, mechanical strength, and wear

resistance of Ti6Al4V-based functionally graded composites.