Microstructure and Mechanical Properties of Hybrid LPBF-DED Inconel 625
Résumé
The hybridization of Laser Powder Bed Fusion and Direct Energy Deposition could increase the application range of additive manufacturing by benefiting from the resolution of LPBF and the flexibility of DED. However, the microstructures and mechanical properties obtained by these processes are very different. This causes the hybrid parts to be very heterogeneous. The mechanical behavior of hybrid LPBF-DED Inconel 625 parts are investigated under static and cyclic loading. Both as-built and heat-treated Inconel 625 are studied to investigate the role of the specific as-built microstructure. Tensile tests are performed using Digital Image Correlation, which allows the global behavior to be explained by the local behavior of the samples. Hybrid samples are also tested under high cycle fatigue, and fractographic observations permit to determine the initiation sites and mechanisms. The DED is found to be the limitation in both the static and the fatigue strengths of hybrid samples. Hybrid samples perform as well as or better than mono-process DED. In static loading, the local behavior of the hybrid samples and the yield tensile strength gap between LPBF and DED determine the global behavior. The heat-treatment is successful in reducing this gap, and improving the global behavior of the hybrid samples, especially the total elongation. In fatigue, the defects are preponderant compared to the mechanical heterogeneity of hybrid samples.