• Krajňák, Tomᡡš
• Dzugan, Jan
• Raghavan, Srinivasan
• Li, Ying
• Podany, Pavel
• Veselý, Jozef
• Koukolíková, Martina

Abstract

<jats:p>The creep properties of a laser-directed energy deposition (L-DED) technique manufactured Inconel 718 (IN718) was investigated at 650 °C/700 MPa. Microstructure and creep properties of L-DED IN718 samples were tailored by various post heat treatments involving homogenization heat treatment with temperature ranging from 1080 to 1180 °C + double aging and hot isostatic pressing (HIP). Microstructural changes and their influence on the creep behavior and fracture mechanism were observed and discussed. The results show that L-DED sample heat treated by a simple double aging exhibits a 49% increase in creep lifetime tr and a comparable creep elongation ɛf when compared to the wrought material, due to the reserved coarse dislocation cell substructure from the L-DED process. The loss of dislocation cell structure and the coarsening of grains at higher temperature of heat treatments contributes to a shorter tr, εf, but faster ε̇min (minimum creep rate). The present work demonstrates that a simultaneous improvement of creep strength and creep elongation can be achieved in the case of a coarse-grained L-DED IN718 by a double aging treatment which can preserve both the strengthening precipitates and an appropriate size of dislocation cells.</jats:p>

Topics

• Deposition
• grain
• strength
• dislocation
• precipitate
• aging
• hot isostatic pressing
• homogenization
• creep
• directed energy deposition
• aging