Abstract:
This study examines the morphological evolution of c0 precipitates in cast CMSX-4 single-crystal Ni-based superalloy subjected to prestraining at either 982 C or room temperature, followed by long-term high-temperature exposure (up to 1185 h at 982 C and 1088 h at 1150 C). Four initial conditions were evaluated: (1) unstrained specimens; (2) specimens prestrained to 2.6% by interrupted creep at 982 C and 250 MPa; and (3–4) specimens prestrained to 0.5% and 1.0% by interrupted tensile testing. In dendrite cores, unstrained and 0.5% prestrained samples exhibited subtle rafting after exposure at 982 C for up to 1185 h. By contrast, 2.6% and 1.0% prestrained specimens developed spontaneous rafting after just 150 h . At 1150 C, all conditions showed partial c0 dissolution. In the 1.0% prestrained sample, subtle rafting appeared after 203 h but degraded with further exposure due to c0 coarsening, while the 0.5% condition displayed only c0 dissolution and coarsening. These results demonstrate that, in cast CMSX-4, both the degree and mode of prestraining, together with exposure temperature and duration, promote instability in the aged c–c0 microstructure and strongly influence the early onset of spontaneous rafting . Although mechanical performance was not assessed in this study, spontaneous rafting is known to contribute to the degradation of mechanical properties under high-temperature service. Overall, the findings show that rafting at 982 C is primarily driven by elastic energy minimisation, whereas at 1150 C interfacial energy becomes dominant, leading to more extensive isotropic c0 coarsening and c0 dissolution.
Referência:
SOUZA, Gabriel Praça de; FANTINI, Luiza de Brito; MOREIRA, Marcelo Ferreira.; AZEVEDO, C.R.F. Effect of prestraining and prolonged high-temperature exposure on y’ precipitate morphology incast CMSX-4 superalloy. International Journal of Metacasting, 18 p., Oct., 2025.
Acesso ao artigo no site do Periódico:
https://link.springer.com/article/10.1007/s40962-025-01772-8