In-situ hybrid Cr3C2 and γ′-Ni3(Al, Cr) strengthened Ni matrix composites: Microstructure and enhanced properties

Abstract

Mechanical properties of Ni-based superalloys strongly depend on γ′-Ni3Al precipitates and hard particles. However, the traditional Ni-based composites have reached the serviceability limit as to satisfy the requirement of higher speed and thrust to weight ratio for advanced aerospace engines. Herein, we successfully fabricated a novel in-situ Cr3C2 particulate combined with γ′-Ni3(Al, Cr) precipitate synergistically reinforced pure Ni matrix composites by reactive hot press techniques. The SEM and XRD results demonstrate that ternary layered Cr2AlC decompose and transform into nonstoichiometric Cr3C2 particles at high temperature, while the additional Al and fractional Cr atoms reacted with Ni matrix to form γ′-Ni3(Al, Cr). Microstructure and mechanical behavior of the as-resulted composite materials in relationship with different fractions of Cr2AlC (10 vol%, 20 vol%, 30 vol% and 40 vol%) are carefully investigated. In 30 vol%Cr2AlC/Ni and 40 vol%Cr2AlC/Ni composites, the in-situ synthesized Cr3C2 particles and γ′ phase are uniformly distributed in the matrix, consequently endowing the composites superior mechanical properties. The flexural strength of 30 vol% and 40 vol% Cr2AlC/Ni composites was 1790 ± 25 MPa and 1752 ± 73 MPa respectively, which is about 7 times higher than the pure Ni matrix. In addition, the tensile strength was determined to be 947 ± 19 MPa and 846 ± 15.9 MPa, respectively. For the substantial reinforcement, the dominant contributions are ascribed to the combined strengthening mechanisms in term of refining the grain, precipitate strengthening and solid-solution strengthening.