Investigation on process stability and repeatability of flow properties and topography of PBF-LB/M manufactured channels

Since the early 2000 s Additive Manufacturing (AM) started to transform from an R& D and prototyping technology to an industrial application to be used in serial production. Especially in the aerospace and turbine industry, AM processes, such as laser based powder bed fusion of metals (PBF-LB/M) were established for flow-sensitive parts. One of the most important aspects of serial production is repeatability. In this paper, the repeatability of circular channels with a focus on flow and topography properties is investigated. A variance analysis was conducted on an EOS M400-4 multi-laser PBF-LB/M machine with the nickel-based super alloy Haynes 282. Flow samples were systematically placed in different positions across the build area. Different channel orientations relative to the build direction and laser center were investigated. A and a layer height were used. Synchrotron computed tomography (CT) scans were conducted on 48 samples and correlated with the results of the flow measurements. While the average effective flow area of vertically manufactured samples was higher than for horizontal samples, the variation between samples increased the more vertical a sample is oriented. It was possible to attribute variations in the effective flow area of the channels to variations of a simple maximum inscribed circle diameter including roughness of the samples. Equations describing the variations of the flow and topography properties for channels in different build orientations were derived. Surface roughness and overprinted material for multiple sample orientations and positions were examined and considerations for the production of flow relevant channels formulated.