The influence of process parameters and heat treatment on γ′ precipitates of selective electron beam melted Ni-based single-crystal superalloy

• Main Authors: Xiyang Guo, Xin Zhou, Peiyu Zhang, Yucong Duan, Xing Cheng, Xuede Wang, Tong Cao, Pei Zhao
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2021-08-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/5.0059160

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.