Abstract
This study focuses on the dwell-fatigue crack propagation behavior of IN718 manufactured via selective laser melting (SLM). The dwell-fatigue test condition is 823 K (550 ^{circ }C) with a long 2160-s dwell-holding period. Effects of heat treatment and loading direction on dwell-fatigue crack propagation rates are studied. A grain boundary delta precipitate seems to be slightly beneficial to the dwell-fatigue cracking resistance of SLM IN718. A comparison has been made between SLM IN718 and forged counterparts at different temperatures, indicating that a creep damage mechanism is likely dominant for SLM IN718 under the present test condition. A general discussion of the inferior creep resistance of SLM IN718 is also included. The anisotropic dwell-fatigue cracking resistance has also been studied and rationalized with the effective stress intensity factor calculated from finite element modeling.
Highlights
SELECTIVE laser melting (SLM) is one of the most widely used additive manufacturing (AM) techniques for metallic materials
Crack paths and fracture surfaces are only compared between the P- and N-type orientations, but not between different heat treatment conditions
The dwell crack generally propagates on the same plane as the pre-crack, and the propagation direction is perpendicular to the loading direction and parallel to the building direction
Summary
SELECTIVE laser melting (SLM) is one of the most widely used additive manufacturing (AM) techniques for metallic materials. For critical Ni-base superalloy engine components, SLM shows overwhelming advantages over other non-AM processes for geometric complexities.[1] The attempts to manufacture Ni-base superalloy (IN718,[2,3,4] IN738LC,[5,6] Hastelloy X,[7,8,9] CM247LC[10,11,12] and IN625[13,14,15] components) via SLM have attracted much attention in the AM field in the past years. The reliability of these SLM Ni-base superalloys under dynamic and complicated service conditions still needs to be demonstrated
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