Mechanism of hot crack propagation and prevention of crack formation during electron beam powder bed fusion of a difficult-to-weld Co-Cr-Ni-W superalloy

2021 ◽  
Vol 293 ◽  
pp. 117088
Author(s):  
M.A.L. Phan ◽  
D. Fraser ◽  
S. Gulizia ◽  
Z.W. Chen
Keyword(s):  
Electron Beam ◽  
Crack Propagation ◽  
Crack Formation ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Hot Crack

scholarly journals Cyclic Crack Growth in Chemically Tailored Isotropic Austenitic Steel Processed by Electron Beam Powder Bed Fusion

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6544
Author(s):  
Matthias Droste ◽  
Ruben Wagner ◽  
Johannes Günther ◽  
Christina Burkhardt ◽  
Sebastian Henkel ◽  
...  
Keyword(s):  
Electron Beam ◽  
Crack Propagation ◽  
Austenitic Steel ◽  
Crack Growth ◽  
Manganese Content ◽  
Growth Behavior ◽  
Austenitic Steels ◽  
Crack Growth Behavior ◽  
Powder Bed Fusion ◽  
Powder Bed

The present study analyzes the cyclic crack propagation behavior in an austenitic steel processed by electron beam powder bed fusion (PBF-EB). The threshold value of crack growth as well as the crack growth behavior in the Paris regime were studied. In contrast to other austenitic steels, the building direction during PBF-EB did not affect the crack propagation rate, i.e., the crack growth rates perpendicular and parallel to the building direction were similar due to the isotropic microstructure characterized by equiaxed grains. Furthermore, the influence of significantly different building parameters was studied and, thereby, different energy inputs causing locally varying manganese content. Crack growth behavior was not affected by these changes. Even a compositional gradation within the same specimen, i.e., crack growth through an interface of areas with high and areas with low manganese content, did not lead to a significant change of the crack growth rate. Thus, the steel studied is characterized by a quite robust cyclic crack growth behavior independent from building direction and hardly affected by typical parameter deviations in the PBF-EB process.

Grain Morphology and Texture Development in a Co-Cr-Mo Alloy Fabricated by Powder Bed Fusion with an Electron Beam

2019 ◽  
Author(s):  
Yufan Zhao ◽  
Yuichiro Koizumi ◽  
Kenta Aoyagi ◽  
Daixiu Wei ◽  
Kenta Yamanaka ◽  
...  
Keyword(s):  
Electron Beam ◽  
Grain Morphology ◽  
Texture Development ◽  
Powder Bed Fusion ◽  
Powder Bed

scholarly journals Comparison of Phase Characteristics and Residual Stresses in Ti-6Al-4V Alloy Manufactured by Laser Powder Bed Fusion (L-PBF) and Electron Beam Powder Bed Fusion (EB-PBF) Techniques

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 796
Author(s):  
Aya Takase ◽  
Takuya Ishimoto ◽  
Naotaka Morita ◽  
Naoko Ikeo ◽  
Takayoshi Nakano
Keyword(s):  
Electron Beam ◽  
Residual Stresses ◽  
Cooling Rate ◽  
Process Parameters ◽  
Phase Evolution ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Solidification Temperature ◽  
Powder Bed ◽  
Β Phase

Ti-6Al-4V alloy fabricated by laser powder bed fusion (L-PBF) and electron beam powder bed fusion (EB-PBF) techniques have been studied for applications ranging from medicine to aviation. The fabrication technique is often selected based on the part size and fabrication speed, while less attention is paid to the differences in the physicochemical properties. Especially, the relationship between the evolution of α, α’, and β phases in as-grown parts and the fabrication techniques is unclear. This work systematically and quantitatively investigates how L-PBF and EB-PBF and their process parameters affect the phase evolution of Ti-6Al-4V and residual stresses in the final parts. This is the first report demonstrating the correlations among measured parameters, indicating the lattice strain reduces, and c/a increases, shifting from an α’ to α+β or α structure as the crystallite size of the α or α’ phase increases. The experimental results combined with heat-transfer simulation indicate the cooling rate near the β transus temperature dictates the resulting phase characteristics, whereas the residual stress depends on the cooling rate immediately below the solidification temperature. This study provides new insights into the previously unknown differences in the α, α’, and β phase evolution between L-PBF and EB-PBF and their process parameters.

scholarly journals Microstructure–property gradients in Ni-based superalloy (Inconel 738) additively manufactured via electron beam powder bed fusion

2021 ◽  
pp. 102121
Author(s):  
Bryan Lim ◽  
Hansheng Chen ◽  
Zibin Chen ◽  
Nima Haghdadi ◽  
Xiaozhou Liao ◽  
...  
Keyword(s):  
Electron Beam ◽  
Powder Bed Fusion ◽  
Powder Bed

scholarly journals Corrosion Fatigue Characteristics of 316L Stainless Steel Fabricated by Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1046
Author(s):  
Balachander Gnanasekaran ◽  
Jie Song ◽  
Vijay Vasudevan ◽  
Yao Fu
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
Fatigue Properties ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Corrosion Properties ◽  
Powder Bed ◽  
Fatigue Characteristics

Laser powder bed fusion (LPBF) has been increasingly used in the fabrication of dense metallic structures. However, the corrosion related properties of LPBF alloys, in particular environment-assisted cracking, such as corrosion fatigue properties, are not well understood. In this study, the corrosion and corrosion fatigue characteristics of LPBF 316L stainless steels (SS) in 3.5 wt.% NaCl solution have been investigated using an electrochemical method, high cycle fatigue, and fatigue crack propagation testing. The LPBF 316L SSs demonstrated significantly improved corrosion properties compared to conventionally manufactured 316L, as reflected by the increased pitting and repassivation potentials, as well as retarded crack initiation. However, the printing parameters did not strongly affect the pitting potentials. LPBF samples also demonstrated enhanced capabilities of repassivation during the fatigue crack propagation. The unique microstructural features introduced during the printing process are discussed. The improved corrosion and corrosion fatigue properties are attributed to the presence of columnar/cellular subgrains formed by dislocation networks that serve as high diffusion paths to transport anti-corrosion elements.

scholarly journals Laser Powder Bed Fusion Processing of Fe-Mn-Al-Ni Shape Memory Alloy—On the Effect of Elevated Platform Temperatures

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 185
Author(s):  
Felix Clemens Ewald ◽  
Florian Brenne ◽  
Tobias Gustmann ◽  
Malte Vollmer ◽  
Philipp Krooß ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Crack Formation ◽  
Microstructural Analysis ◽  
Tensile Load ◽  
Grain Structure ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Cyclic Heat Treatment ◽  
Powder Bed ◽  
Cyclic Heat

In order to overcome constraints related to crack formation during additive processing (laser powder bed fusion, L-BPF) of Fe-Mn-Al-Ni, the potential of high-temperature L-PBF processing was investigated in the present study. The effect of the process parameters on crack formation, grain structure, and phase distribution in the as-built condition, as well as in the course of cyclic heat treatment was examined by microstructural analysis. Optimized processing parameters were applied to fabricate cylindrical samples featuring a crack-free and columnar grained microstructure. In the course of cyclic heat treatment, abnormal grain growth (AGG) sets in, eventually promoting the evolution of a bamboo like microstructure. Testing under tensile load revealed a well-defined stress plateau and reversible strains of up to 4%.

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