Prakt. Met. Sonderband 47 (2015) 43 
Fig. 8: Detailed view of Fig. 7 
3 Discussion, Conclusions, Recommendations 
Basically, the metallurgical root cause of the failure is solidification cracking that is induced upon 
cooling after casting, immediately prior to complete solidification, when the thermal stresses from 
cooling cannot be withstood by still liquid films of interdendritic liquid; hence the dendritic fracture 
appearance. These findings are consistent with the microstructure exhibiting actually two parallel 
cracks (Fig. 5) and are also consistent with the findings of the first investigation. 
Since hot tearing in steel castings made of G20MnS5 is a well-known phenomenon, according to 
some sources, and is mainly caused by low cooling and solidification rates after casting, it is 
recommended to place gating systems away from highly loaded areas. Gating systems are thermal 
centers and are associated with low cooling rates. Another option is an alteration of the material 
selection. G16Mo3, 1.5415 could be chosen instead, or G42CrMo4, 1.7231 per EN 10293. These 
materials are less prone to hot tearing than G20MnS5. 
S Summary 
One out of eight lifting lugs of a large gas turbine engine exhibited indications upon magnetic 
particle surface crack inspection (MT), that were later verified by ultrasonic testing (UT). The 
subject part was made of a low-alloy steel casting. It had already been used in service and was 
supposed to be re-used, together with the other lifting lugs of the set. In order to determine the cause 
of the indications, non-destructive metallographic examinations by means of the replica technique 
were performed. In that investigation, the indications were determined to have been caused by 
crack-like decohesions of material. In one of the examined areas, these imperfections were 
associated with small casting defects, namely micro shrinkage. This might have contributed to crack 
initiation. The described small surface cracks at the cylindrical part of the lifting lug itself were 
probably caused by bending stresses in service. Indications were found only on one out of the entire 
set of eight parts. There. only the upper side of the short spigot, were axial tension on the surface is