Abstract
The Ni-7.9Cr-5.9W-22.2Mo-1.4Ti superalloy based on Ni-8Cr-6W-22.5Mo (the Haynes 244 alloy) was prepared to investigate the effect of Ti addition on the precipitation behavior and mechanical properties. The results indicate that the addition of Ti can facilitate the formation of C11b and D022 superlattice phases simultaneously after age-treated at 650 °C for 240 h. The yield strength is significantly improved to 1645 MPa compared with Ni-8Cr-6 W-22.5Mo with only the formation of C11b and a yield strength of 1297 MPa. The excellent strengthening effect of C11b and D022 superlattice phases are attributed to both order strengthening and coherency strengthening, and their calculated contributions to strengthening are 148 MPa and 439 MPa for D022 and 83 MPa and 208 MPa for and C11b, respectively. Together with solid-solution strengthening and grain refinement strengthening, the theoretically calculated yield strength matches well with the experimental results. In addition, the deformation mode changes from deformation slip to strain-induced twinning after the Ti addition.
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