Strength prediction of Ni-base disc superalloys: Modified γ′ hardening models applicable to commercial alloys

The reported strength predictions of gamma ' hardening so far for polycrystalline Ni-base superalloys tend to be underestimated. This is mostly due to the difficulty in isolating the gamma ' hardening amidst the complicated multi-level strengthening mechanisms of the alloy and negligence of the contribution from gamma/gamma ' mixture strength. For these reasons, a series of single-crystal tie-line model alloys with specially designed gamma ' size and volume fractions was adopted in this work, allowing a direct validation of classical gamma ' particle hardening equations for the first time. Using the iso-work assumption, gamma ' particle strengthening and gamma/gamma ' mixture strength at 650 degrees C were individually extracted from the compression test results. It was found that the classical strengthening models were unable to predict the expected strength increment with increasing gamma ' volume fractions. Modified versions of the classical equations were proposed, which gave improved predictability across wider gamma ' volume fractions and served as important basis for strength design application.

Automated summary

The reported strength predictions of gamma ' hardening for polycrystalline Ni-base superalloys tend to be underestimated, with a need for validated classical strengthening models and proposed modifications to improve predictability.