Modeling of strain-age cracking in precipitation hardened nickel-based alloys

Strain age cracking (SAC) in precipitate hardening nickel-based alloys caused by heat treatments or reheating in multi-pass welds is of major concern when designing high performance components.

The problem become even more pronounced for alloys that precipitates rapidly and have an elevated volume fraction of precipitates. Some alloys are even treated as “non-welable”.

In principle, it is possible to design any component with an optimal shape through the use of additive manufacturing, however, such manufacturing technique triggers SAC.

Hence, it is of a high interest to increase knowledge and improve lifetime predictions for components susceptible to SAC.

Such efforts would, for instance, make it possible to produce more efficient and lighter jet-engines, which would contribute to reduce NOx emissions.Currently, three main theories exist in the literature trying to explain the key mechanism for SAC, where the role of negative misfit strains is one of them.

Owing to the fact that the interplay with the responsible mechanisms for SAC is not clear, the aim of this project is to thoroughly evaluate the role of misfit strains on SAC during clustering, nucleation and growth of precipitates in precipitate hardened Ni-based alloys.

Our theory is that negative misfit strains exist in a certain temperature range and alloy composition, and is the key mechanisms for SAC. To validate the developed models, high energy X-ray synchrotron experiments at the nanometer scale will bed performed.