Residual stress-induced distortions in laser powder bed additive manufacturing of nickel-based superalloys

Abstract

One of the significant process limits of laser powder bed additive manufacturing technologies is residual stresses and distortions induced by heating the fine metal powder to the melting point and sudden cooling to the initial temperature. While this phenomenon applies to most types of metal alloys, it becomes more important in nickel-based superalloys, which have low thermal conductivity and high-quality requirements for aerospace utilization. Together with the mechanical integrity and geometric problems in the final product, residual stress-induced distortions carry the potential risk of interrupting the job process above a certain distortion limit as a result of part-to-re-coater rubbing. Process simulations performed in a computer environment are of critical importance to predict and to prevent this risk. However, simulation models need to be verified through experiments, and they need to be cost-effective in terms of simulation times. This paper presents a comprehensive study to introduce a fast thermo-mechanical simulation model, together with experiments on nickel-based superalloy demonstrators. It also contributes to the scientific knowledge base with novel coupon design, manufacturing and evaluation methodology for distortion studies.