Effect of scan pattern on the microstructure and mechanical properties of Powder Bed Fusion additive manufactured 17-4 stainless steel

Kudzal, Andelle; McWilliams, Brandon; Hofmeister, Clara; Kellogg, Frank B.; Yu, Jian; Taggart-Scarff, Joshua; Liang, Jianyu

doi:10.1016/j.matdes.2017.07.047

Cited by 147 publications

(54 citation statements)

References 33 publications

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“…Therefore, the initial temperature difference between the molten pool and the previously solidified surface is larger, which leads to a higher cooling rate of horizontal samples and refinement of austenite grains. The laser scanning strategy can change the thermal history of each layer, thus affecting the porosity and microstructure of L-PBF parts [129]. Although the energy density input to the powder bed remains unchanged, the total distance that the laser travels varies with the strategy due to the geometric constraints of the specific scanning strategy.…”

Section: Gas-atomizedmentioning

confidence: 99%

“…In addition, the scanning time of each layer is also different. Six different laser scanning strategies are shown in Figure 8 [129]. Except for the hexagonal scanning strategy, the grains of all scanning strategies were textured along the build direction due to the repetitive nature of the line scanning strategy.…”

Section: Gas-atomizedmentioning

confidence: 99%

“…Except for the hexagonal scanning strategy, the grains of all scanning strategies were textured along the build direction due to the repetitive nature of the line scanning strategy. Table 3 [129] shows the average austenite fraction corresponding to different scanning strategies. 1 The hexagon pattern ("hexagon") consists of 25-mm-diameter hexagonal islands with a 100-µm overlap of hexagons within the layer.…”

Section: Gas-atomizedmentioning

confidence: 99%

“…Factors including powder surface, particle shape, particle size, and flowability of the powder can affect the bulk density of powder [130]. Density of the L-PBF parts is often measured using a method based on Archimedes' law [115,125,129]. Hu [131] demonstrated that scan speed and slice thickness have a significant impact on the L-PBF part's density.…”

Section: Defectsmentioning

confidence: 99%

“…A larger volume of low-viscosity molten liquids induced by higher heat input is formed in the powder bed, which may lead to a better wettability and subsequently enhance the densification [132]. The scanning strategy does not have very much influence on densification of L-PBF parts, but it can lead to different roundness and area distribution of holes [129]. Table 5.…”

Section: Defectsmentioning

confidence: 99%

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Laser Powder Bed Fusion of Precipitation-Hardened Martensitic Stainless Steels: A Review

Zai

Zhang

Wang

et al. 2020

Metals

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Martensitic stainless steels are widely used in industries due to their high strength and good corrosion resistance performance. Precipitation-hardened (PH) martensitic stainless steels feature very high strength compared with other stainless steels, around 3-4 times the strength of austenitic stainless steels such as 304 and 316. However, the poor workability due to the high strength and hardness induced by precipitation hardening limits the extensive utilization of PH stainless steels as structural components of complex shapes. Laser powder bed fusion (L-PBF) is an attractive additive manufacturing technology, which not only exhibits the advantages of producing complex and precise parts with a short lead time, but also avoids or reduces the subsequent machining process. In this review, the microstructures of martensitic stainless steels in the as-built state, as well as the effects of process parameters, building atmosphere, and heat treatments on the microstructures, are reviewed. Then, the characteristics of defects in the as-built state and the causes are specifically analyzed. Afterward, the effect of process parameters and heat treatment conditions on mechanical properties are summarized and reviewed. Finally, the remaining issues and suggestions on future research on L-PBF of martensitic precipitation-hardened stainless steels are put forward.Metals 2020, 10, 255 2 of 25 types of microstructures can be obtained with different heat treatment processes [9]. The typical temperature range for aging heat treatment for this alloy is 480-620 • C [1]. Under the H900 condition (aging temperature: 482 • C, time: 1 h), the precipitation in 17-4 PH stainless steel begins with Cu-rich precipitates (bcc, body center cubic) that maintain a coherent relationship with the matrix, which would lead to an increase in tensile strength and toughness [4]. These precipitates can transform into non-coherent Cu-rich particles (fcc, face center cubic) after extended aging at 400 • C [5]. After experiencing over-aging, the precipitates are coarsened. The number of precipitates is reduced, and the coherence relationship is also destroyed [6,10]. These changes together lead to a decrease in mechanical strength, but an increase in ductility and impact toughness.PH stainless steels are widely used in the aerospace industry [11,12], the marine industry [13], nuclear reactor components [14], chemical process equipment [15], and medical apparatus due to their high tensile strength, impact strength, fracture toughness, and corrosion resistance at typical service temperatures below 300 • C [15,16]. Most of these parts are important load-bearing components of heavy machinery in a demanding service environment. However, PH stainless steels have poor workability and machinability due to their high strength and high hardness, which result in a long production cycle and difficulties in obtaining desired shapes through conventional machining and forming processes [17].Due to the high strength and high hardness of PH steels, they are difficult to b...

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Section: Gas-atomizedmentioning

confidence: 99%

Section: Gas-atomizedmentioning

confidence: 99%