Synergistic effects of TC4 and heat treatment on the microstructure, mechanical properties, and high-temperature oxidation properties of laser-deposited GH4169 alloys

This study systematically investigates the synergistic effects of Ti–6Al–4V (TC4) addition and homogenization plus dual aging (HA) heat treatment on the microstructure, tensile properties, and high-temperature oxidation resistance of GH4169 alloys fabricated via laser melting deposition (LMD). Microstructural analysis demonstrates that TC4 addition reduces grain size and Laves phase length, while HA treatment promotes δ-Ni 3 Nb phase precipitation and Laves phase dissolution. Crystallographic orientation analysis reveals a coherent relationship between γ and γ′ phases, but an incoherent relationship between γ and γ″ phases. Tensile tests indicate that HA treatment not only enhances tensile strength but also improves the elongation of the 5TC4/GH4169 composite, yielding a 45% increase in yield strength (from 738 MPa to 1070 MPa) and a 28% rise in elongation (from 17.5% to 22.4%). This improvement is primarily attributed to precipitation strengthening and dislocation strengthening mediated by finer γ′ and γ″ precipitates. High-temperature oxidation tests at 800 °C show that the synergy of TC4 and HA treatment reduces mass gain by 9% (from 0.45 mg cm −2 to 0.41 mg cm −2 ) and lowers the oxidation rate to 1.99 × 10 −8 mg 2 cm −4 s −1 , indicating enhanced oxidation resistance due to a continuous Nb 2 O 5 –TiO 2 –NiO–Al 2 O 3 oxide layer. These findings highlight the efficacy of TC4 reinforcement and tailored thermal processing in optimizing Ni-based alloys for additive manufacturing applications.