EFFECTS OF B AND P ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF GH984 ALLOY

The Ni-Fe based superalloy GH984 with microalloying is fabricated by vacuum induction furnace and hot worked by hot forging and rolling.The effect of B and P microaUoying on microstructure and mechanical properties of GH984 alloy was investigated by OM,SEM and TEM after standard heat treatment.The experiment results showed that the addition of B and P has no obvious effects on the microstructure of GH984 alloy which has precipitates of sphericalγ',Ti(C,N), blocky MC as well as discrete M_(23)C_6 distributing along grain boundary.Moreover,the addition of B and P has no obvious influence on the tensile strength at room temperature and 700℃.However, tensile ductility increases greatly at 700℃after B and P doping.It is worth to note that B and P microslloying can improve the stress rupture life of the alloy significantly.For example,the rupture life at the condition of 700℃.and 350 MPa increases from initial 115.03 h to 984.15 h.Investigation on the microstucture of the creep samples exhibites that B and P could effectively improve the strength of grain boundary and the fractural model from intergranular fracture to intergranular/transgranular mixed fracture.