断口附近组织对GH4080A合金缺口持久性能的影响

Effects of Microstructure Near Fracture Zone on Notch Stress Rupture Properties of GH4080A Alloy

以630℃汽轮机紧固件备选合金GH4080A合金为研究对象,对美国Special Metals Company(SMC)和抚顺特钢(FG)冶炼的材料经过标准热处理后分别在不同载荷下进行高温缺口持久试验,并结合光学显微镜(OM)和扫描电镜(SEM)及背散射电子衍射(EBSD)分析,研究合金持久寿命的分散性与持久样品断口附近组织的关联性。结果表明:GH4080A FG边缘和芯部持久寿命不同的主要原因是两者晶粒大小不同,FG芯部的晶粒尺寸最大,持久寿命最强。FG边缘与SMC边缘持久寿命不同的主要原因是两者变形机制不同,前者为晶界滑移,后者为晶内变形与晶界变形协调作用。

Taking GH4080A alloy as an alternative alloy for fastener application the steam turbine running at the temperature near 630℃high-temperature notch stress rupture tests under different loads were carried out on the standard heat treated materials which were melted from Special Metals Corporation(SMC)and Fushun Special Metal Company(FG).Then,the relationship between characteristics of microstructure near facture zone and the dispersivity of rupture life was investigated by OM,SEM and EBSD analysis.The results show that the difference of rupture life for specimens melted from FG is mainly due to the different grain size distribution at edge and at the center of the billet bar.The grain size of the core parts of FG is the largest and the rupture life is the strongest.The reason for the difference of rupture life for specimens at the billet bar edge melted from FG and SMC is the different deformation mechanisms under rupture loads.Grain boundary sliding is the dominant deformation for specimens melted from FG,while the dominant deformation for specimens melted from SMC is the coordination between grain boundary sliding and intracrystalline plastic deformation.