Control of Solidification Structure of Stainless Steel in Additive Manufacturing Process

Gas atomization is a widely used method to produce the raw powder materials for additive manufacturing (AM) usage. After the metal alloy is melted to fusion, gas atomization involves two relatively independent processes: liquid breakup and droplet solidification. In this paper, the solidification behavior of powder during solidification is analyzed by testing the powder’s properties and observing microstructure of a martensitic stainless steel (FeCrNiBSiNb). The powder prepared by gas atomization has high sphericity and smooth surface, and the yield of qualified fine powder is 35%. The powder has typical rapid solidification structure. Collision between powders not only promotes nucleation, but also produces more satellite powder. The segregation of elements in powder is smaller as the result of high cooling rate which can reaches 4.2 × 105 K/s in average. Overall, the powder prepared by gas atomization is found to have good comprehensive properties, desired microstructure, and accurate chemical component, and it is suitable for various additive manufacturing techniques.

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Preliminary characterization of phenomena occurring during single track fabrication in laser additive manufacturing of stainless steel

International Congress on Applications of Lasers & Electro-Optics ◽

10.2351/1.5063130 ◽

2014 ◽

Author(s):

Ville-Pekka Matilainen ◽

Heidi Piili ◽

Antti Salminen ◽

Tatu Syvänen ◽

Olli Nyrhilä

Keyword(s):

Stainless Steel ◽

Additive Manufacturing ◽

Single Track ◽

Laser Additive Manufacturing ◽

Preliminary Characterization

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Microstructure and Crystallographic Texture of Laser Additive Manufactured Nickel-Based Superalloys with Different Scanning Strategies

Crystals ◽

10.3390/cryst11060591 ◽

2021 ◽

Vol 11 (6) ◽

pp. 591

Author(s):

Xingbo Liu ◽

Hui Xiao ◽

Wenjia Xiao ◽

Lijun Song

Keyword(s):

Additive Manufacturing ◽

Epitaxial Growth ◽

Crystallographic Texture ◽

Continuous Wave ◽

Flow Direction ◽

Fiber Texture ◽

Laves Phase ◽

Solidification Structure ◽

Columnar Grains ◽

Scanning Strategies

Control of solidification structure and crystallographic texture during metal additive manufacturing is a challenging work which attracts the increasing interest of researchers. In the present work, two kinds of scanning strategies (i.e., single-directional scanning (SDS) and cross-directional scanning (CDS) were used to control the solidification structure and crystallographic texture during quasi-continuous-wave laser additive manufacturing (QCW-LAM) of Inconel 718. The results show that the solidification structure and texture are strongly dependent on scanning strategies. The SDS develops a typical fiber texture with unidirectional columnar grains, whereas the CDS develops a more random texture with a mixture of unidirectional and multidirectional grains. In addition, the SDS promotes the continuously epitaxial growth of columnar dendrites and results in the linearly distributed Laves phase particles, while the CDS leads to the alternately distributed Laves phase particles with chain-like morphology and discrete morphology. The changed stacking features of molten-pool boundary and the switched heat flow direction caused by different scanning strategies plays a crucial role on the epitaxial growth of dendrites and the final solidification structure of the fabricated parts.

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