Influence of Microstructure, in Particular Grain Size, on the Low Cyle Fatigue Behavior at Service Temperature of the Superalloys X40, UDIMET 500, in 738 LC and INCONEL 739

摘要

The microstructure of cast turbine blades can show a wide variation between different castings. The following tests were made to investigate the effect of microstructure on fatigue LCF tests on UDIMET 500, INCONEL 738 LC, X 40 and INCONEL 939 were performed on material with large and with small grain sizes. Crack propagation tests were performed on UDIMET 500, X 40 and INCONEL 738 LC. Different grain sizes were tested. In the LCF tests the large grain size gives superior properties in material INCONEL 739 and X 40 while LCF properties in material UDIMET 500 and INCONEL 738 LC appear to be insensitive to grain size. In the crack propagation tests there is no significant difference in propagation rate between the different grain sizes. Difference in the LCF properties may not be grain sizes but other structural variables. For X 40 the morphology of the carbide phase might be the most important factor. In INCONEL 739 there is a greater probability for interdendritic fracture in the small grain size material and this may be the reason for the difference in the LCF properties. (ERA citation 04:050298)