Effect of inclusion size and distribution on Low Cycle Fatigue properties of an FGH97 superalloy

Abstract:

Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Metallographic Microscope and Low Cycle Fatigue testing machine were used to study the relationship between the Low Cycle Fatigue performance of 650 °C/ maximum stress 980MPa and the size, area ,distribution of fracture inclusions of a nickel-based FGH97 superalloy. The results show that the low-cycle fatigue fracture is mainly casued by non-metallic inclusions. If the size or area of the non-metallic inclusions is less than a critical value（about 80μm）, there is no significant effect on the low cycle fatigue life of 650 ℃/ maximum stress 980MPa , and the average life value reaches 190,992 cycles. The distribution of inclusions has no significant influence on the low cycle fatigue life when the size is less than the critical value of 80μm.When the size exceeds the critical value, the larger size of inclusion and the closer to surface result in the lower the low cycle fatigue life.

Key words:FGH97 P/M superalloy; Microstructure; Low Cycle Fatigue; Inclusion