Microstructure and scratch properties of GO/TC4 composites by selective laser melting

Ti6Al4V (TC4) alloys are attractive for aerospace, biomedical, and automotive applications; however, their poor tribological performance and persistent strength–ductility trade-off restrict reliable service under complex loading conditions. This study aims to improve the microstructural stability and scratch resistance of TC4 by incorporating graphene oxide (GO) through selective laser melting (SLM). GO/TC4 composite powders were first prepared via an electrostatic self-assembly strategy to ensure uniform reinforcement dispersion, and the composites were subsequently fabricated under optimized SLM parameters(100 W laser power, 300 mm/s scanning speed, 70 um hatch spacing, and 25 um layer thickness). Microstructural characterization, particularly HRTEM analysis of the 0.54 wt.% sample, suggested the presence of localized rGO/TiC/α-Ti interfacial features, which may contribute to microstructural refinement and improved interfacial compatibility. Among the investigated compositions, the 0.27 wt.% GO/TC4 composite exhibited the best overall performance, achieving a relative density of 98% with a superior balance between indentation hardness and modulus. Scratch testing showed that this sample maintained a stable and low friction coefficient of approximately 0.23 under a 1 N load, while the interfacial shear model displayed a strong linear correlation (R 2 >0.95), indicating that friction was mainly governed by tribofilm shearing rather than severe matrix plowing. Raman analysis further confirmed that stress-induced rGO fragmentation facilitated the formation of a continuous sacrificial lubricating film. In contrast, excessive GO addition (0.54 wt.%) caused agglomeration, reduced densification, and interfacial decohesion. Overall, the incorporation of 0.27 wt.% GO provides an effective strategy for improving the scratch resistance and surface durability of SLM-fabricated TC4 composites. • GO/TC4 composites were successfully fabricated by SLM using electrostatic self-assembly-assisted powder preparation. • SLM-fabricated 0.27 wt.% GO/TC4 achieved a relative density of 98%. • HRTEM of the 0.54 wt.% sample suggested localized rGO/TiC/α-Ti interfacial features after SLM. • The optimal composite showed stable scratch resistance through tribofilm shearing and stress-induced rGO lubrication.