Optimization of the Post Heat Treatment of Additively Manufactured IN718
Alber Sadek, EWI, Columbus – Ohio, USA
IN718 has good fabricability, high strength at elevated temperature, and corrosion resistance, and it is widely deployed in many aerospace and other high-performance applications. With the molten pool rapid solidification during L-PBF, the resulting microstructure is anisotropic and inhibits macro-segregation. The as-built condition usually exhibits lower mechanical properties. Four different heat treatment procedures were designed and tested to study the effect of different heat treatment parameters on the type of precipitates and grain size.
The investigated heat treatment procedures showed the formation of equiaxed grain size and a significant amount of g' and g" particles at the grain boundary in addition to MC carbides. Three types of microstructure characteristics and grain size were achieved.
- Coarse grain size suitable for creep application was achieved by increasing the soaking time at the aging cycle.
- The formation of serrated grain boundaries suitable for good fatigue and creep properties was achieved by decreasing the stress relief cycle's soaking time and temperature.
- Fine-grain size, which is preferable for fatigue properties, was achieved by decreasing the soaking time at the solution annealing cycle.