Effect of Powder Recycling in Electron Beam Melting on the Surface Chemistry of Alloy 718 Powder
Journal article, 2019

Process-induced degradation of the powder feedstock in additive manufacturing may have a negative influence on the final properties of built components. Consequently, it may lower the cost-effectiveness of powder bed additive manufacturing, which relies on recycling of the nonconsumed powder. This is especially the case for production of high-performance aero engine components where high material and process reliability is required. This study comprises a detailed investigation on the degradation of Alloy 718 powder during multicycle electron beam melting (EBM). The surface-sensitive analysis methods, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), were combined with scanning electron microscopy (SEM) to depict the differences in surface morphology, and surface composition of powder samples exposed to varying numbers of re-use cycles. The results show a significant change in surface characteristics after exposing the powder to the process and the environment in the build chamber. The virgin powder is covered mainly by a relatively thin and homogeneous oxide layer. The re-used powder, however, has undergone transformation to a heterogeneous oxide layer, rich in thermodynamically stable Al-rich oxide particulates, which started already during the first build cycle. Significant growth of the Al-rich oxide occurs via selective oxidation of Al under the conditions in the build chamber, including both pick-up of oxygen from the process atmosphere and redistribution of initial surface-bound oxygen from less-stable products like Ni-oxide and/or hydroxide.

Author

Hans Gruber

Chalmers, Industrial and Materials Science, Materials and manufacture

Mikael Henriksson

Chalmers, Industrial and Materials Science, Materials and manufacture

Eduard Hryha

Chalmers, Industrial and Materials Science, Materials and manufacture

Lars Nyborg

Chalmers, Industrial and Materials Science, Materials and manufacture

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

1073-5623 (ISSN)

Vol. 50 9 4410-4422

Subject Categories

Manufacturing, Surface and Joining Technology

Materials Chemistry

Metallurgy and Metallic Materials

DOI

10.1007/s11661-019-05333-7

More information

Latest update

2/12/2021