During manufacturing of rotor disks made from titanium- or nickel-base alloys events rarely may happen that lead to local mechanical or thermal overload of tool or workpiece material. These events can cause anomalies that are assumed to initiate crack growth. Breakage of the machining tool cutting edge can lead to residual tool particles being embedded in the component surface. Another anomaly type is local overheating, damaging the micro-structure of the material. It was observed that in nickel-base material Inconel 718 overheating may lead to a significant rise of magnetic permeability and generation of magnetic remanence which may be caused by the formation of a ferromagnetic phase. The paper presents experimental results of AC and DC electromagnetic methods to detect and characterize these anomalies. The magnetic remanence method, based on fluxgate gradiometers, can record the residual field of the anomalies even from a certain distance. Magnetic particle inspection technique lets recognise the shape of ferromagnetic surface anomalies. High resolution eddy current probes are able to visualise these anomalies even without magnetizing them. Additionally, test blocks with graded anomalies are presented to compare the performance of these non-destructive inspection methods.
Detection and characterization of magnetic anomalies in gas turbine disks
Nachweis und Charakterisierung von magnetischen Anomalien in Gasturbinenscheiben
2006
11 Seiten, 14 Bilder, 11 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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