Title

Intergranular fatigue crack growth in P/M superalloy material at elevated temperatures

Document Type

Conference Proceeding

Date of Original Version

12-1-2009

Abstract

The influence of microstructure, in particular secondary gamma prime precipitates, γ′S, on intergranular cracking of the P/M IN100 is investigated. A series of heat treatments using coupons made of as-received material is carried out in order to identify conditions leading to minimum and maximum variation in the size and volume fraction of secondary gamma prime, γ′S. These specific heat treatments are applied to compact tension specimens to regenerate the corresponding γ′S statistics. In addition to these microstructures, specimens subjected to extended aging time as well as long thermal exposure at 650°C have been generated and characterized. Fatigue crack growth experiments are performed on compact tension specimens having as received as well as modified microstructures at both 650°C and 700°C in air. The loading cycle includes a dwell time ranging from 100 seconds to 7200 seconds and superimposed at the maximum load level. Results of the as received material show that the length of the dwell time does not influence the crack growth rate. Results of the heat treated microstructures at 650°C showed that a reduced volume fraction of γ′S enhances the growth rate. The influence of the volume fraction of γ′S on altering the intergranular crack growth rate is explained in terms of the crack tip stress relaxation.

Publication Title

12th International Conference on Fracture 2009, ICF-12

Volume

8

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