Progress Towards Qualification of Metal Additive Manufacturing
Interest in the application of Additive Manufacturing (AM) to a wide range of manufacturing problems has generated significant worldwide investment and activity. Its promise of integrating different materials systems and producing component designs not possible through subtractive processing routes has led to many claims of the transformative nature of this technology. However, the field currently relies on the use of conventional materials systems that have not been designed for the conditions under which AM processes operate. In addition, the extreme processing conditions create inhomogeneous materials that can include intense localized compositional gradients. elongated microstructures. pronounced crystallographic texture. highly anisotropic local and macroscopic stresses. and non-equilibrium phases. Typically. such as-built parts require substantial post-build thermal and thermo-mechanical processing to achieve the consistent, predictable mechanical properties required for fracture-critical applications. Unfortunately. traditional heat treatments rely upon consistent starting microstructures that are radically different from many AM-built materials. To meet the full potential that AM has to offer. especially for flight-critical components (e.g. rotating parts, fracture-critical parts. etc.), qualification and certification efforts are necessary. This overview highlights some of the key aspects regarding materials qualification needs across the AM spectrum. While development of qualification standards will address some of these needs, this overview outlines some of the other key areas that will need to be considered in the qualification path, including various process-, microstructure-, and fracture-modeling activities in addition to integrating these with lifing activities targeting specific components.