表面再结晶对单晶高温合金SRR99中温持久性能及断裂行为的影响

摘要

利用喷丸预变形,研究了表面再结晶对SRR99单晶高温合金中温持久性能及断裂行为的影响.结果表明,表面再结晶对单晶合金中温持久寿命影响很大,760℃ /785 MPa条件下,厚度约为103μm的再结晶层(约占试样横截面面积8％)使合金中温持久寿命下降了约90％.再结晶层几乎没有承载能力,基体承受的实际应力增大,是导致合金持久性能下降的主要原因.此外,再结晶层与基体界面处的缺口效应也会使合金的持久寿命进一步降低.760℃/785MPa条件下,未再结晶试样的微观断裂方式为微孔聚集型断裂与滑移剪切断裂共存的混合型断裂,而再结晶试样则以纯滑移剪切的方式断裂.%The influence of surface recrystallization on the intermediate-temperature stress rupture property and fracture behavior of single crystal superalloy SRR99 was investigated by shot peening. The results show that the intermediate-temperature stress rupture property of the single crystal superalloy was greatly influenced by surface recrystallization. A recrystallized surface layer with the depth of a-bout 103 μm, accounting for about 8% of the fracture surface, resulted in a decrease in stress rupture life by nearly 90% . The recrystallized layers nearly have no bearing capacity, and as a result, the actual stress on the matrix increases, which is the main reason of the remarkable decrease in stress rupture life. In addition, the notch effect resulting from recrystallization makes the stress rupture life decrease further. Under 760t /785MPa, the unrecrystallized specimens fracture under the co-effect of mierovoid coalescence and shear by slip, while the fracture mode of the recrystallized specimens is pure shear fracture by slip.