Development and characterization of graphene-reinforced Inconel 825 composite alloy for high temperature applications

In this work, a composite alloy consisting of Inconel 825, tungsten carbide (WC), cobalt (Co), and graphene (Gr) is developed and characterized. It is made by layer-by-layer sintering and spark plasma sintering processes at temperatures between 950 and 1,050°C and pressures between 40 and 50 MPa. The four different compositions that were made were 94.85 wt% Inconel–4.5 wt% WC–0.5 wt% Co–0.15 wt% Gr, 45 wt% Inconel–10 wt% WC–33 wt% Co–12 wt% Gr, 33 wt% Inconel–10 wt% WC–45 wt% Co–12 wt% Gr, and 90 wt% Inconel–4 wt% WC–5 wt% Co–1 wt% Gr. Detailed surface morphology, chemical analysis, and mechanical property assessments were performed on the resultant specimens. Strong interfacial bonding and low porosity were confirmed by the microstructural investigation, which showed dense composites with relative densities ranging from 96.5 to 97.8%. Specimens with higher Co and WC content had the highest hardness values, measuring 373.33 ± 3.5 HV (specimen C) and 362.75 ± 3.2 HV (specimen A). Superior strength was shown in tensile tests; specimen D (90 wt% Inconel) achieved 763.386 MPa at ambient temperature and dropped to 662.34 MPa at 450°C. This was mainly because of compositional changes like carbon oxidation and the development of Ni₃ precipitate intermetallic phases. A decrease in tungsten carbide stability at higher temperatures was also verified by the study. Mechanical performance was further impacted by elemental diffusion and oxidation effects that were discovered by EDAX analysis of shattered specimens. These results show that Inconel 825 composites’ high-temperature mechanical performance and thermal stability can be considerably improved by an optimized reinforcing content, which qualifies them for use in high-temperature and aerospace applications.