细晶处理对镍基合金疲劳蠕变交互作用行为的影响

本文研究了两种晶粒度的GH 698合金在700℃疲劳蠕变交互作用下的断裂寿命和形变行为.结果表明:在疲劳蠕变应力交互作用下的断裂寿命可以分成F,FC和C三个区.在FC及C区,交变应力的存在明显地阻碍蠕变形变过程,提高了断裂寿命.细晶处理后使这种阻碍作用加强,断裂寿命提高幅度变大.在大应力的疲劳区进行细晶处理,反而使合金寿命降低.     

迭加压应力过载对镍基合金疲劳蠕变交互作用的影响

本文研究了压应力过载峰(S_P)对GH698镍基高温合金700℃下疲劳蠕变交互作用的影响.S_P约在0至-400MPa范围时,断裂周次因存在S_P而增加.当S_P过大或过小时,断裂周次减小.动态蠕变速率的变化和断裂周次呈相反的对应关系.研究表明,S_P的作用表现在四个方面,即减小动态蠕变速率;促进疲劳损伤,引起断裂模式变化;延缓裂纹扩展和产生S_P本身的疲劳损伤.这些作用的强弱随基载循坏应力及S_P值的大小而异.     

压应力过载峰的时间间隔对镍基合金疲劳蠕变交互作用的影响

本文研究了迭加压应力过载峰S_P的时间间隔△t对镍基高温合金GH 698在700℃下疲劳蠕变交互作用的影响.结果表明,随着△t的逐渐减小,加剧合金的疲劳损伤,扩大了断口上疲劳断裂模式的范围,抑制沿晶蠕变断裂模式,这种变化对断裂寿命有明显影响.与此同时,迭加S_P对动态蠕变速率ε及疲劳裂纹扩展速率dα/dN的影响均表现为正反两个方面.当△t较短时,加速动态蠕变与裂纹扩展的因素起主导作用,导致寿命缩短;当△t较长时,则反之.     

Relationship between Grain Size and Fatigue-Creep Interaction Behaviour of Superalloy GH698

The deformation and fracture behaviourof nickel-base superalloy GH698 with differentgrain size have been studied at 700℃ underfatigue-creep interaction conditions. Comparedwith coarse-grained specimens, the grain refiningprocess shows obvious effect on the mechanicalbehaviour of the alloy, i. e. in F and C zones,the fraction of pure fatigue and creep fractureon fracture surfaces is greatly reduced, whichdecreases and increases the fracture life inzones F and C respectively, in FC and C zones,creep deformation is greatly restrained by thealternating stress component, which increasesthe fracture life remarkably. It is also provedthat in spite of the difference in microstru-tures such as grain size, for a constant tem-perature, a unique life equation t_r=A~n canbe used to predict rupture life within the stressregion controlled by the same fracture mode.