Microstructural evolution and tribological performance of SiC-reinforced FGH95 superalloy composites fabricated by spark plasma sintering

Abstract

Abstract

FGH95–SiC composites containing 2.5–10 vol% SiC were fabricated by high-energy ball milling followed by spark plasma sintering (SPS). The effects of SiC content on the microstructure, crystallographic characteristics, hardness, and tribological behavior were systematically investigated. X-ray diffraction analysis confirmed the retention of the γ/γ′ matrix phases and SiC without detectable reaction products after SPS. The calculated γ/γ′ lattice misfit continuously decreased from 0.745% for monolithic FGH95% to 0.567% for the composite containing 10 vol% SiC, although a slight non-monotonic variation of the individual γ and γ′ lattice parameters was observed at the highest SiC content. Etched SEM observations and statistical grain-size analysis revealed only a slight decrease in average grain size from 1.15 ± 1.2 μm for FGH95 to 1.01 ± 1.0 μm for the 10 vol% SiC composite, with substantial overlap among the grain-size distributions. All specimens exhibited relative densities above 98%, indicating near-full densification, while the Vickers hardness increased from approximately 470–575 HV with increasing SiC content. Under sliding wear conditions, the wear rate decreased from approximately 5.2 × 10 −4 to 2.9 × 10 −4 mm 3 N −1 m -1 , corresponding to an improvement of approximately 45% at 10 vol% SiC. The worn-surface morphology revealed a transition from severe abrasive–delamination wear in monolithic FGH95 to predominantly mild abrasive wear in the SiC-reinforced composites. The enhanced wear resistance is primarily associated with the increased hardness and load-bearing capability of the uniformly dispersed SiC particles, together with the high densification and improved γ/γ′ crystallographic compatibility.