High strain-rate behaviour of as-cast and as-build Inconel 718 alloys at elevated temperatures
Daniele Forni, Federico Mazzucato, Anna Valente, Ezio Cadoni
Abstract
The restoration of Inconel 718 components through conventional processes typically require cost-intensive machining operations. Moreover, the refurbishment and reuse are extremely important in structural components likely to be subjected to harsh operating conditions (dynamic loads and elevated temperatures). That is why additive manufacturing processes are rising as disruptive techniques for the restoration of Inconel 718 components. However, a limited number of studies have evaluated the mechanical properties of this nickel-base superalloy in harsh conditions. The objective of this study is to evaluate the coupled effect of strain-rates (0.001, 200 and 800 s−1) and temperatures (20, 350 and 550 °C) on Inconel 718 additive manufactured samples produced by Direct Energy Deposition. A raw Inconel 718 material for the preparation of as-cast samples has been also investigated, and the mechanical results have been compared. The mechanical characterisation at high strain-rates has been performed through a SHTB equipped with a water-cooled induction heating system. Similar mechanical behaviour has been observed between samples realised with a power laser of 400 W and as-cast samples. A gradual decrease of the mechanical strengths is observed for increasing temperatures. The calibration of the Johnson-Cook strength model highlighted the necessity of using specific thermal softening values as a function of fixed strain-rate and temperature.