Effect of build location on microstructural characteristics and corrosion behavior of EB-PBF built Alloy 718

P Karimi,E Sadeghi,P Harlin,J Ålgårdh,J Andersson

doi:10.1007/s00170-019-04859-9

P Karimi, E Sadeghi + Show 3 more

Open Access

https://doi.org/10.1007/s00170-019-04859-9

Copy DOI

Abstract

Electron beam-powder bed fusion (EB-PBF), a high-temperature additive manufacturing (AM) technique, shows great promise in the production of high-quality metallic parts in different applications such as the aerospace industry. To achieve a higher build efficiency, it is ideal to build multiple parts together with as low spacing as possible between the respective parts. In the EB-PBF technique, there are many unknown variations in microstructural characteristics and functional performance that could be induced as a result of the location of the parts on the build plate, gaps between the parts and part geometry, etc. In the present study, the variations in the microstructure and corrosion performance as a function of the parts location on the build plate in the EB-PBF process were investigated. The microstructural features were correlated with the thermal history of the samples built in different locations on the build plate, including exterior (the outermost), middle (between the outermost and innermost), and interior (the innermost) regions. The cubic coupons located in the exterior regions showed increased level (~ 20 %) of defects (mainly in the form of shrinkage pores) and lower level (~ 30-35 %) of Nb-rich phase fraction due to their higher cooling rates compared to the interior and middle samples. Electrochemical investigations showed that the location indirectly had a substantial influence on the corrosion behavior, verified by a significant increase in polarization resistance (Rp) from the exterior (2.1 ± 0.3 kΩ.cm2) to interior regions (39.2 ± 4.1 kΩ.cm2).

Highlights

Additive manufacturing (AM) processes can build parts using computer-aided design (CAD) drawing through stacking layers on top of the others [1, 2]
The aim of the present study is to investigate the location dependency of material properties built by the Electron beam-powder bed fusion (EB-PBF) process where several parts are simultaneously built on the build plate in one batch
The observation of columnar grains is very common in EB-PBF built Alloy 718, in agreement with various literature [10, 16, 26]

Summary

Introduction

Additive manufacturing (AM) processes can build parts using computer-aided design (CAD) drawing through stacking layers on top of the others [1, 2]. Apart from the machine-related parameters such as scanning speed, beam current, focus offset, line offset, etc., the positionrelated parameters which are linked to the type of stacking or orientations of the parts on the build plate must be carefully monitored [10]. These parameters consist of (a) distance between the parts on the build plate, (b) height of the part from the build plate, (c) location of the parts on the build plate, and (d) angle of the parts on the build plate [10]–[12]. Microstructure and resulting properties of the EB-PBF manufactured parts have been observed to be affected by some

Objectives

Results

Conclusion