Abstract
Fully reversed axial loading fatigue tests were conducted using type 420J1 martensitic stainless steel. The specimens were additively manufactured by a laser metal deposition (LMD) process. The results were compared with conventionally manufactured (CMed) type 420J2 stainless steel. According to the axial loading fatigue test results, the fatigue strengths of the laser-metal-deposited (LMDed) specimens were nearly comparable to those of the CMed specimens. Fractographic analyses revealed that process-induced defects were hardly seen at the fatigue crack initiation sites of the LMDed specimens. It indicates that defect-free deposition was possible by the LMD process. On the other hand, when the LMD specimens experienced intervals during deposition processes, local softening occurred due to the tempering of the building plate. Fatigue tests revealed that the interval during LMD process had detrimental effect on the fatigue strengths due to the local softening. The upper and lower bounds of S-N curves were proposed as fatigue design curves for the samples with and without the interval during LMD process.
Highlights
Additive manufacturing (AM) is an attractive method to fabricate near-net-shape components with complex shapes [1],[2]
Fractographic analyses revealed that processinduced defects were hardly seen at the fatigue crack initiation sites of the LMDed specimens
Fatigue tests revealed that the interval during laser metal deposition (LMD) process had detrimental effect on the fatigue strengths due to the local softening
Summary
Additive manufacturing (AM) is an attractive method to fabricate near-net-shape components with complex shapes [1],[2]. Yadollahi et al conducted axial loading fatigue tests and fatigue crack propagation tests using AMed 17 − 4 precipitation hardening stainless steel. They revealed that fatigue cracks predominantly initiated at process-induced defects, such as lack-of-fusion defects, and fatigue lives were successfully predicted using linear elastic facture mechanics assuming crack growth from initial defects. Bandyopadhyay et al investigated fatigue properties and effect of building conditions in Ti6Al-4V fabricated by laser engineered net shaping (LENSTM) [18], one of DED processes, but researches about fatigue of the laser-metal-deposited (LMDed) high strengths stainless steels are missing
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