Formation Mechanism of Streaks in GH4169 Alloy Blades and Its Effect on Blade Fatigue Life
During the surface corrosion inspection of a batch of GH4169 alloy rotor blades,it was found that there were stripes on the surface of the blade body.The formation mechanism of stripes and its influence on the blade fatigue life were analyzed.The results show that the stripes on the blade surface are coarse-grained bands and inclusion aggregation bands distributed along the forging streamline,which are inherited from the smelting process.There are two types of inclusions,one is carbonitride of Ti and Nb,and the other is composite inclusions with MgAl2O4 as the core.When the particle size of the inclusions in the stripes is less than 5 μm,and the grain size difference between the coarse-grained band and the matrix is less than ASTM grade 2,such stripes have little effect on the fatigue life of the blade.High temperature recrystallization two-stage annealing after low temperature aging at δ phase precipitation peak and hot rolling can effectively refine the grains of GH4169 alloy.
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