In-situ (Nb,Ti)C particles reinforced Ni0.6CoFe1.4Nb0.05 medium-entropy alloys

In-situ (Nb,Ti)C particles reinforced Ni0.6CoFe1.4Nb0.05 medium-entropy alloy composites (MEACs) are successfully fabricated by vacuum induction melting technology in this work. The synthesis mechanism of (Nb,Ti)C as well as the effect of its content on the microstructure evolution, mechanical performances and wear behaviors of composites were systematically analyzed. By doping Ti and C elements into Ni0.6CoFe1.4Nb0.05 MEA, the as-cast structure evolved from the initial BCC + FCC to FCC + BCC + (Nb,Ti)C and then to BCC + (Nb,Ti)C. The thermodynamics analysis showed that TiC preferentially precipitated and then acted as a nucleation site for NbC to promote the in-situ formation of multiphase (Nb,Ti)C carbides. Compared with Ni0.6CoFe1.4Nb0.05 alloy, the micro-hardness and the tensile strength of the composites significantly improved with the volume fraction of (Nb,Ti)C increases. The wear behaviors showed that the friction coefficient of composites decreased monotonously, as well as the wear rate first reduced and then raised with the increase of (Nb,Ti)C content. The underlying strengthening and wear mechanisms were also discussed. It is expected that the results will provide a new guidance for designing the MEAs containing multiple reinforced particles.