DZ40M钴基高温合金的中温蠕变形变与断裂

CREEP DEFORMATION AND FRACTURE OF DZ40M COBALT-BASE SUPERALLOY AT INTERMEDIATE TEMPERATURE

本文研究了新近开发的定向凝固ＤＺ４０Ｍ钴基高温合金在７００℃，３６０－３４０ＭＰａ时蠕变形变特点，用扫描电镜和透射电镜分别观察了蠕变断裂断口、纵向剖面和形变后组织结构．结果表明：ＤＺ４０Ｍ合金７００℃起始蠕变阶段蠕变应变和间呈线性关系；稳态蠕变速率可用ε＝Ａ ｅｘｐ（ｂ／ｋＴ）来表示，其中 Ａ＝８．７２７０×１０－１３％ｈ－１ ｂ＝０．９０３９×１０－２１ｃｍ３·ＤＺ４０Ｍ合金表现出高的蠕变塑性；在蠕变过程中，大量细小的 Ｍ２３Ｃ６在基体中沉淀析出，它们有效地强化合金基体； 蠕变断裂为穿晶韧性断裂，裂纹萌生于初生碳化物本身以及与基体的界面裂纹在垂直应力轴方向上扩展，最终导致穿晶断裂。

Creep deformation and fracture of directionally solidified cobalt-base superalloy DZ40M have been investigated at 700℃ under stress with the scope of 360-340 MPa. The creep fracture surfaces and longitudinal sections of crept specimens have been examined by SEM and the deformed microstructures have been observed under TEM. The results showed that there was a linear relationship between transient creep strain () and creep time t1/3, and steady creep rate() could be expressed as = Aexp(b/kT) where, A=8.7270×10-13 % h-1, b=0.9039×10-21 cm3. DZ40M alloy edsbited high creep ductility. In the matrix, a great amount of fine M23C6 carbide precipitated that strengthened the alloy matrix effectively. Creep cracks initiated at primary carbides and interfaces between the carbides and the mains. Cracks propagated transgranularly at the direction perpendicular to the applied stress.