It was found that the cracks appeared on the surface of DD6 single crystal turbine blade platform after testing.Based on the cracks character

the platform failure mode was studied by appearance check

observation on fracture surfaces

microscopic structure examination

and chemical analysis.The results show that the cracks have made from the surface recrystallization of DD6 single crystal turbine blade platform;it has relation to the grain boundary face.Under stress condition

the cracks have expensed along the white particles bond until fatigue failure.Meanwhile

it was found that the recrystallization zone already exists at its surface before application.Owing to the larger cast stress during cast process

the carbide is formatted in platform zone.Then

the recrystallization grain

which mass precipitated phases with W element are around its boundary

is formatted in heat treatment.