Effect of solution aging treatment on high and very high cycle fatigue properties of nickel-based alloy fabricated by laser powder bed fusion at 25 °C and 650 °C

Heat treatment is an effective post-treatment method for improving the mechanical properties of additive manufacturing (AM) materials by adjusting the microstructure, refining the grain and eliminating residual stress. However, its effect on the fatigue properties of AM materials is not yet well understood. Here, combined with some testing technologies such as 2D & 3D microscopies and electron backscatter diffraction, the axial loading tests with stress ratio of −1 at 25 °C and 650 °C are performed to examine the effect of solution aging treatment on the high & very high cycle fatigue properties of the nickel-based alloy fabricated by laser powder bed fusion (L-PBF). The fatigue properties of L-PBF nickel-based alloy are improved mainly due to the dissolution of the laves phase and the precipitation of strengthening phases. Internal fatigue failure is promoted at elevated temperature, and three types of internal crack nucleation mechanisms are revealed. The zigzag growth path of microcracks corresponds to the process of crystallographic facets formation. The phase transformation process and strengthening mechanisms are explained. Finally, a fatigue life prediction model is proposed, and the prediction results are in good agreement with the experimental results.