| Summary: | γ′ precipitates, the main strengthening phase of Ni-based single-crystal superalloys, are
difficult to determine in the forming zone of selective electron beam melting (SEBM),
which is best for realizing the direct manufacturing of single crystal superalloys.
Herein, the relationship between parameters and γ′ precipitates is urgently needed to be
fabricated, and solution heat treatment is an efficient way to obtain a desired uniform γ′
microstructure. In the initial work, an array of SEBM experiments with various processing
parameters were carried out, the processing window and parameter influence on γ′
precipitates were fabricated successfully, and a solution heat treatment protocol was
applied for obtaining a homogeneous γ′ microstructure in the as-built SEBM microstructure.
In processing, the bulks can be manufactured with a beam current of 10–12.4 mA and a scan
speed of 1.7–2.4 m/s. The dimensions of the γ′ precipitates present regular changes with
parameters such as current and scan speed, and a great change had also been observed in
building height. After the heat treatment includes recovery-annealed (1100 °C, 6 h),
solution-treated (1300 °C, 0.5 h), and aged (1100 °C, 6 h + 870 °C, 5 h) precipitates, the
size of γ′ precipitates gradually increases and homogenizes, and an optimized solution and
aging heat treatment protocol was established.
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