Deleterious Intergranular Phases in Nickel Alloy 725: Detection, Identification and Quantification

Abstract

Alloy 725 is used in critical oil and gas equipment. However, failures have occurred, evidencing the lack of understanding of the role played by microstructure and the limitations of the current regulations. This work found a distinctive microstructural feature in failed batches. Specifically, failed batches had a significant extent of F phase at grain boundaries, which increased cracking susceptibility. Additionally, the method developed to detect such microstructures may serve as a new qualification test.