B和P对GH984合金组织和力学性能的影响

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

利用真空冶炼制备了微合金化Ni-Fe基GH984合金并热锻、轧制成棒材,采用OM,SEM和TEM观察了标准热处理后B和P微合金化GH984合金的微观组织,并研究了B和P微合金化对合金力学性能的影响.结果表明:B或P的微合金化对GH984合金中的析出相影响不大,合金中的析出相为γ′相、Ti(C,N)相、MC型和M_(23)C_6型碳化物.然而,B和P同时添加使M_(23)C_6型碳化物形貌由块状向粒状转变并均匀分布于晶界;B和P的添加对合金的室温和700℃拉伸强度无明显影响,但可成倍提高合金的高温拉伸塑性.持久寿命随B和P的添加显著提高,此外,相对单独添加B,B和P的同时添加可以更好地改善合金的持久性能.持久试样的断口观察表明,B和P微合金化明显改善了晶界强度,断裂模式由沿晶断裂转变为混合断裂.

The Ni-Fe based superalloy GH984 with microalloying is fabricated by vacuum in- duction furnace and hot worked by hot forging and rolling. The effect of B and P microalloying 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 spherical .y/, Ti（C, N）, blocky MC as well as discrete M23C6 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.