Cyclic Deformation Behavior of Additive-Manufactured IN738LC Superalloys from Virgin and Reused Powders

Abstract

In laser powder bed fusion (L-PBF), most powders are not melted in the chamber and collected after the printing process. Powder reuse is appreciable without sacrificing the mechanical properties of target components. To understand the influences of powder reuse on mechanical performance, a nickel-based superalloy, IN738LC, was investigated. Powder morphology, microstructure and chemical compositions of virgin and reused powders were characterized. An increase in oxygen content, generally metallic oxides, was located on the surface of powders. Monotonic tensile and cyclic fatigue were tested. Negligible deterioration in strength and tensile ductility were found, while scattered fatigue performance with regard to fatigue life was shown. Deformation and fatigue crack propagation mechanisms were discussed for describing the powder degradation effects.

Characterization, preparation, and reuse of metallic powders for laser powder bed fusion: a review

“…Similar to the steel, the change of composition in the reused Inconel 718 alloy powders seems to be limited to the increase of oxygen content [35,199,201,234], while the variation of other elements, such as C, N, and H, is marginal [182,194,199,234]. The increased oxygen content is in the form of Cr, Al, and Ti-rich oxides with a size of several micrometers [35,182,201] attaching to the surface layer of reused Inconel 718 powders. As for the microstructure of Hastelloy X powders [198], both the virgin and reused powders show no obvious texture (figures 12(a-i) and (a-iii)).…”

“…There is no obvious microstructure variation, including grain size, dendrite size, and texture, when reusing the Inconel 718 or Inconel 738 powders [182,199,201]. For instance, it is found that the L-PBF Inconel 718 samples printed with both virgin and reused powders exhibit continuous γ matrix and flower-shaped γ ′ precipitates, as well as similar texture and grain size [234] (figures 12(b-i) and (b-iii)).…”

“…• Ti6Al4V [183] • Inconel 718 [182] • Formation of irregular-shaped spatters [191] Marginal change • Inconel 718 [194] • Inconel 738 [201] • Ti6Al4V [181,204] • AlSi10Mg [193,205,208,210] NA Flowability Increase • 304L [195],…”

“…Due to its poor machinability, nickel-based superalloys, such as Inconel 718 [230], Inconel 738 [231], Inconel 625 [232], or Hastelloy X alloy [233], are frequently investigated for L-PBF due to the advantage of near-net shaping. To reduce the fabrication cost and improve the powder usage efficiency, there are already some investigations on powder reuse for L-PBF nickel alloys [35,42,174,182,194,198,199,201,234,235].…”

“…Gruber et al [194] observed that the hardness of samples prepared using reused Inconel 718 powders decreased marginally from 334 HV to 329 HV. When the room temperature tensile properties are referred to, different evolution trends have been obtained for L-PBF parts printed with reused Inconel 718 or Inconel 738 powders [182,199,201,234]. Chen et al [201] observed that samples prepared using virgin and reused Inconel 718 powders exhibited nearly identical UTS, YS, and elongation.…”