The Creep Behavior of Additively Manufactured Inconel 625

Creep tests of additively manufactured (AM) Inconel 625, both hot isostatically pressed (HIPed) and non-HIPed, are performed at various stresses between 65 and 658 MPa at 650-800 degrees C. The creep behavior of AM samples are compared with that of (conventional) wrought alloys. Tests are performed over a 24 h period for initial heat-treated samples and also after heat exposure at the service temperature of 650 degrees C for 6 months. The 6 month tests consist of a time-temperature profile similar to Inconel 625 service conditions in jet engines. It is found that the creep strength of AM 625 has equal or superior creep strength at 650-800 degrees C compared with the wrought alloy, even after 6 months exposure to the test temperature. The HIPed AM alloys has significantly superior ductility over the non-HIPed AM Inconel 625, as expected. However, the ductility of the HIPed AM Inconel 625 is still substantially lower than the wrought alloy, particularly at the longer exposure times to the test temperatures. The explanation for the dramatic loss of ductility is not clearly identified, but sulfur segregation to grain boundaries and relatively higher oxygen content leading to oxide embrittlement are the possibilities.