Effect of the process atmosphere composition on alloy 718 produced by laser powder bed fusion
Journal article, 2021

The detrimental effect of nitrogen and oxygen when it comes to the precipitation of the strengthening γ’’ and γ’ phases in Alloy 718 is well-known from traditional manufacturing. Hence, the influence of the two processing atmospheres, namely argon and nitrogen, during the laser powder bed fusion (L-PBF) of Alloy 718 parts was studied. Regardless of the gas type, considerable losses of both oxygen of about 150 ppm O2 (≈30%) and nitrogen on the level of around 400 ppm N2 (≈25%) were measured in comparison to the feedstock powder. The utilization of nitrogen as processing atmosphere led to a slightly higher nitrogen content in the as-built material—about 50 ppm—compared to the argon atmosphere. The presence of the stable nitrides and Al-rich oxides observed in the as-built material was related to the transfer of these inclusions from the nitrogen atomized powder feedstock to the components. This was confirmed by dedicated analysis of the powder feedstock and supported by thermodynamic and kinetic calculations. Rapid cooling rates were held responsible for the limited nitrogen pick-up. Oxide dissociation during laser–powder interaction, metal vaporization followed by oxidation and spatter generation, and their removal by processing atmosphere are the factors describing an important oxygen loss during L-PBF. In addi-tion, the reduction of the oxygen level in the process atmosphere from 500 to 50 ppm resulted in the reduction in the oxygen level in as-built component by about 5%.

Oxygen content

Nitrogen

Process gas

Alloy 718

Additive manufacturing

Argon

Laser powder bed fusion

Author

Camille Nicole Géraldine Pauzon

Chalmers, Industrial and Materials Science, Materials and manufacture

Andreas MarkstrÖm

Thermo-Calc Software AB

Sophie Dubiez Le Goff

Linde GmbH

Eduard Hryha

Chalmers, Industrial and Materials Science, Materials and manufacture

Metals

2075-4701 (eISSN)

Vol. 11 8 1254

Subject Categories

Materials Chemistry

Other Chemistry Topics

Metallurgy and Metallic Materials

DOI

10.3390/met11081254

More information

Latest update

8/24/2021