服役损伤对汽轮机末级叶片断裂性能的影响

对服股１０年的汽轮机末级叶片材料进行了力学性能实验，并与未服役的新叶片材料进行对比。结果表明服役材料弹性模量Ｅ、断裂韧度Ｊ０．２及ＪＲ阻力曲线以及冲击韧度ＡＫ都有所下降，而静拉伸的伸长率及断面收缩率有所升高。以上变化主要反映在裂纹萌生阶段，微观分析表明服役材料在服股载荷作用下有些夹杂或第二相与基体脱离形成了微空洞损伤，服役材料的微观应力减小及位错组态变化都是导致上述性能变化的原因。

THE EFFECT OF SERVICE DAMAGE ON FRACTURE MECHANICAL PROPERTIES OF THE LAST STAGE BLADE IN A STEAM TURBINE

Fracture mechanics tests were carried out for the last stage blade material from a steam turbine after ten year service and comparison tests were carried out for the same virgin material.The results showed that the elastic modulus, E ,impact work, A K ,fracture toughness, J 0.2 ,and R curve for the old material were lower than those for the virgin material.The tensile elongation and the reduction of area of the old material were higher than those of the virgin material.The differences mentioned above mainly appeared in the stage of crack nucleation.The microscopy observation and microstress testing results indicated that the formation of voids and the lowering of microstress and the variation of dislocation configuration in the old material lead to the changes of the fracture behavior.