EFFECT OF Mg AND Zr ADDITION ON CREEP CRACK GROWTH BEHAVIOUR OF A Ni-BASE SUPERALLOY

The creep crack growth(CCG)and the time to carck initiation and rupture of specimen(t_(rc)and t_r)were measured by means of electrical potential method on single edge notchedspecimens at 700℃.The field near the crack tip under steady-state creep was represented byenergy rate integral(C~*),and the CCG rate as a function of C~* has been obtained.Theagreement between the predicted and observed t_(rc)values is quite good.It was found that theaddition of small amount of Mg and Zr in the alloys causes t_(rc)and t_r of the specimens to in-crease significantly.