Influence of scan strategy and process parameters on microstructure and its optimization in additively manufactured nickel alloy 625 via laser powder bed fusion

Laser powder bed fusion (LPBF) can fabricate products with tailored mechanical and surface properties. In fact, surface texture, roughness, pore size, the resulting fractional density, and microhardness highly depend on the processing conditions, which are very difficult to deal with. Therefore, this paper aims at investigating the relevance of the volumetric energy density (VED) that is a concise index of some governing factors with a potential operational use. This paper proves the fact that the observed experimental variation in the surface roughness, number and size of pores, the fractional density, and Vickers hardness can be explained in terms of VED that can help the investigator in dealing with several process parameters at once.

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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 ◽

10.3390/cryst11070796 ◽

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.

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Role of laser powder bed fusion process parameters in crystallographic texture of additive manufactured Nb-48Ti alloy

Journal of Materials Research and Technology ◽

10.1016/j.jmrt.2021.06.054 ◽

2021 ◽

Author(s):

Rafael de Moura Nobre ◽

Willy Ank de Morais ◽

Matheus Tavares Vasques ◽

Jhoan Guzmán ◽

Daniel Luiz Rodrigues Junior ◽

...

Keyword(s):

Process Parameters ◽

Crystallographic Texture ◽

Fusion Process ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

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Optimizing Laser Powder Bed Fusion Parameters for IN-738LC by Response Surface Method

Materials ◽

10.3390/ma13214879 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4879

Author(s):

Mireia Vilanova ◽

Rubén Escribano-García ◽

Teresa Guraya ◽

Maria San Sebastian

Keyword(s):

Response Surface ◽

Response Surface Method ◽

Process Parameters ◽

Crack Density ◽

Processing Parameters ◽

Optimum Process ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Surface Method

A method to find the optimum process parameters for manufacturing nickel-based superalloy Inconel 738LC by laser powder bed fusion (LPBF) technology is presented. This material is known to form cracks during its processing by LPBF technology; thus, process parameters have to be optimized to get a high quality product. In this work, the objective of the optimization was to obtain samples with fewer pores and cracks. A design of experiments (DoE) technique was implemented to define the reduced set of samples. Each sample was manufactured by LPBF with a specific combination of laser power, laser scan speed, hatch distance and scan strategy parameters. Using the porosity and crack density results obtained from the DoE samples, quadratic models were fitted, which allowed identifying the optimal working point by applying the response surface method (RSM). Finally, five samples with the predicted optimal processing parameters were fabricated. The examination of these samples showed that it was possible to manufacture IN738LC samples free of cracks and with a porosity percentage below 0.1%. Therefore, it was demonstrated that RSM is suitable for obtaining optimum process parameters for IN738LC alloy manufacturing by LPBF technology.

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