δ phase precipitation in cast alloy IN625 with varied Cr content and associated properties

The cast alloy IN625 has been developed recently and evaluated as a candidate material for 700°C class advanced ultrasupercritical plants. In order to clarify the effects of chromium (Cr) on δ phase precipitation and mechanical properties of cast alloy IN625, aging treatment experiments on cast alloy IN625 with different chromium additions were carried out. It was revealed that the precipitation of the δ phase in cast alloy IN625 after aging at 750°C was nearly unaffected by chromium content. The tensile properties of cast alloy IN625 appeared to be insensitive to chromium content but were sensitive to the δ phase. Stress rupture tests showed that the rupture time of aged alloys increased compared with those of the solid solution alloys. Moreover, when the fraction of the δ phase increased from 18 to 35%, different trends emerged in the stress rupture life at 400 and 375 MPa, respectively.