Modelling Creep and Creep Crack Growth of LPBF alloy 718

Components manufactured by laser powder bed fabrication (LPBF) are fundamentally limited by their performance for use in critical applications. With respect to high temperature materials produced via LPBF, microstructural defects - such as unfavourable precipitate formation, suboptimal grain size and distribution - and macroscale anomalies - like lack of fusion, intra/inter layer defects - often result in LPBF components performing well below their wrought counterparts.

In this work, alloy 718 parts, fabricated using a quad-laser Renishaw machine with different scanning strategies, build orientations and number of lasers, were
creep tested at 650 under a 600 MPa load. For a given strategy, a 24% increase in creep life compared to wrought alloy 718 was observed. The build 0rientation was also shown to be a determining factor in the creep failure mechanism.

Modelling of creep and Creep crack growth work is underway. It is therefore possible, as a result of this work, to propose build strategies for high temperature creep applications and be able to accurately predict LPBF alloys creeep performance.