Defect Analysis of "White Spot" in GH4169G Low Pressure Turbine Disc Forgings

The macroscopic and microscopic features of abnormal and normal areas were compared and analyzed in view of the "white spot" defect of low-pressure turbine disc forgings of an aeroengine. The results show that the abnormal area is the "white spot" produced by visible lean Nb segregation, and its macroscopic size exceeds 8 mm technical requirements. The grain size of abnormal region is 2 grade, which exceeds the technical requirement of 10 grade. There is a mass of inclusions near the "white spot", the inclusions are oxide inclusions of Mg and Al. According to the analysis results combined with the ultrasonic C-scanning map of the forging, the monitoring measures from raw materials, disc billet and forgings were put forward.