微孔在一种三代镍基单晶高温合金热处理及持久试验过程中的演化

Evolution of micro-pores during heat treatment and stress rupture testing in a third-generation nickel based single crystal superalloy

利用扫描电镜、Image Pro Plus软件和Nano Measurer软件研究了微孔在铸态、固溶处理态和完全热处理态的一种三代镍基单晶高温合金中的形貌及尺寸,采用蠕变试验机研究了微孔在合金持久试验过程中的演化。结果表明:铸态合金枝晶间区域γ/γ′共晶边缘存在少量的不规则形状的微孔,微孔的体积分数约为0.09%,平均尺寸约为9.54μm;经固溶处理后合金中会产生圆形和方形的固溶微孔,固溶处理(1325℃)时间由4 h延长到8 h,固溶微孔的体积分数由0.42%增加到0.46%,增加了约10%。时效处理对固溶微孔的体积分数没有明显影响。固溶微孔会在合金持久过程中发展为裂纹源,最终导致持久断裂,方形微孔更易发展成裂纹。

Morphology and size of micro-pores in a third-generation nickel based single crystal superalloy in as cast,solution treated and fully heat treated states were studied using scanning electron microscopy,Image Pro Plus software and Nano Measure software.The evolution of micro-pores during stress rupture test of the alloy was studied using creep testing machine.The results show that there are a small number of irregularly shaped micro-pores at theγ/γ′eutectic edge of the interdendritic region of the as cast alloy,with a volume fraction of about 0.09%and an average size of about 9.54μm.After solution treatment,round and square shape solid solution micropores will be generated in the alloy.When the solution treatment time(1325℃)is extended from 4 h to 8 h,the volume fraction of solid solution micro-pores increases from 0.42%to 0.46%,an increase of about 10%.The aging treatment has no significant effect on the volume fraction of solid solution micro-pores.Solid solution micro-pores will develop into crack sources during the stress rupture tests of the alloy,ultimately leading to creep rupture,and square micro-pores are more likely to develop into cracks.