Holistic view of additive manufacturing of blade integrated disks in the context of aerospace certification

The production of safety class one blade integrated disks (blisks) traditionally involves costly and time-consuming methods, utilizing precision machining of a solid forged block of nickel-based alloy in compliance with DIN EN 9133. This conventional approach, while meeting stringent certification requirements for turbine components operating under extreme conditions (900-1400 °C), suffers from increased tool wear due to milling solid blocks, leading to design limitations impacting efficiency. In this context, layer-by-layer construction using Additive Manufacturing (AM) processes, such as laser-based powder bed fusion of metals (PBF-LB/M), enable a resource-efficient process with a high level of design freedom. Process-related support structures typical for the PBF-LB/M process must be subsequently separated using subtractive processes, whereby the synergy and implications of integrating additive and subtractive manufacturing on the certification process has been insufficiently researched. The component properties of PBF-LB/M components exhibit greater deviations compared to conventional manufacturing methods as a result of local remelting and the associated complex temperature fields, complex machine transferability and reproducibility. In this work, the integration of additive manufacturing into the existing process chain was investigated. Considering the aerospace certification of safety class one components, a holistic process chain from the digital component model to the finished part was developed, which consists of design definition, additive manufacturing, heat treatment, subtractive post-processing and referencing as well as quality assurance along the entire process chain. We investigated the interdependencies of the various work steps in the process chain and the transfer of certification requirements in accordance with the conventional production route. The divergence in input material (powder), data preparation methods (support structures), machine maintenance, manufacturing complexity (dimensional accuracy), and component properties (reproducibility) poses significant challenges in applying established standards. Additionally, the absence of regulatory guidelines within the aerospace sector and specific OEM directives for additive manufacturing complicates the comprehensive evaluation of the alternative approach proposed. A better understanding of the complex interplay of various factors impacting additive manufacturing is crucial to promote OEM acceptance. However, due to this complexity, a final validation requires the integration of OEMs and the official institutes such as DIN, ISO, ASTM and EN to assess and create alternative standards. The combination of additive manufacturing and subtractive manufacturing may change the nature of BLISK manufacturing for aerospace in the near future, ensuring high-performance and efficient aviation.