Fig. 1 The last stage blade
The blade with cracks is the second last stage blade of low pressure
rotor of 350MW supercritical unit(Fig. 1), made of 17-4PH (China brand
05Cr17Ni4Cu4Nb), which is a martensitic precipitation hardening
stainless steel with solution + aging. During the overhaul in July 2018,
it was found that 80 of the 98 moving blades of the second last stage of
low-pressure rotor had cracks near the root, near the top and in the
middle of the blade back arc.
The cracking mechanism of the low-pressure rotor blades is analyzed in
this paper in order to find out the causes of the defects and make
preventive measures.