Fatigue Crack Growth in Maraging Steel Obtained by Selective Laser Melting

Abstract

Selective Laser Melting (SLM) is an additive manufacturing technology, ideal for the production of complex-shaped components. Design against fatigue is fundamental in the presence of cyclic loads, particularly for these materials which typically have significant porosity, high surface roughness and residual stresses. The main objective here is to study fatigue crack growth (FCG) in the 18Ni300 steel obtained by SLM. Typical da/dN-ΔK curves were obtained in C(T) specimens, indicating that cyclic plastic deformation may be the controlling mechanism. A complementary analysis, based on plastic CTOD range, showed a relatively low level of crack tip plastic deformation, and consequently a reduced level of plasticity induced crack closure. The curve da/dN versus plastic CTOD range is clearly above the curves for other materials.

Numerical tool for the analysis of CTOD curves obtained by DIC or FEM

“…These 138 points were obtained numerically for a CT specimen made of 18Ni300 steel, with a width W = 36 mm, a crack length a = 20.272 mm and a thickness of 0.1 mm. 26 The specimen was submitted to F max = 49.61 N and F min = 5 N. The CTOD was measured at the first node behind crack tip. The first point in Figure 2 corresponds to the minimum load, which is followed by a progressive increase of load up to its maximum value and by the subsequent return to its minimum value.…”

“…representation of CTOD versus load curve, including the identification of characteristic points. B, Parameters for fatigue crack growth analysis F I G U R E 2 Original data points of CTOD versus load (CT specimen, W = 36 mm, a = 20.272 mm, plane stress, F max = 49.61 N, F min = 5 N, 18Ni300 steel) 26 [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…Figure 2 presents the set of numerical points used to describe the algorithm, which are listed in Appendix A. These 138 points were obtained numerically for a CT specimen made of 18Ni300 steel, with a width W = 36 mm, a crack length a = 20.272 mm and a thickness of 0.1 mm 26 . The specimen was submitted to F max = 49.61 N and F min = 5 N. The CTOD was measured at the first node behind crack tip.…”

“…Original data points of CTOD versus load (CT specimen, W = 36 mm, a = 20.272 mm, plane stress, F max = 49.61 N, F min = 5 N, 18Ni300 steel) 26 [Colour figure can be viewed at wileyonlinelibrary.com]…”

Wire Arc Additive Manufacturing of Stainless Steels: A Review

“…Metal additive manufacturing processes utilize laser beam, electron beam, or arc as the heat source and the feedstock material is in the form of powder, wire, or sheet [1,10]. AM processes used for metals mainly include powder bed fusion (PBF) [11][12][13][14][15], directed energy deposition (DED) and sheet lamination (SL) [10]. The commonly used metal AM processes include PBF-L (powder bed fusion utilizing a laser as the heat source) [16][17][18][19][20][21][22][23][24][25], DED-GMA (directed energy deposition with gas metal arc), and DED-L (directed energy deposition using laser beam as the heat source) [26,27].…”