Thermal aging effects on the microstructure of Nb-bearing nickel based superalloy weld overlays using ultrasound techniques

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Victor Hugo C. de Albuquerque (Author) FEUP; Cleiton Carvalho Silva (Author) Other; Paulo G. Normando (Author) Other; Elineudo P. Moura (Author) Other; João Manuel R. S. Tavares (Author) FEUP

Journal

Title: MATERIALS & DESIGN

Vol. 36

Pages: 337-347

ISSN: 0261-3069

Publisher: Elsevier Science

Indexing

ISI Web of Knowledge - 22 Citations

ISI Web of Science

Scopus - 29 Citations

COMPENDEX

INSPEC

Scientific classification

FOS: Engineering and technology

CORDIS: Technological sciences

Other information

Authenticus ID: P-002-BJA

DOI: 10.1016/j.matdes.2011.11.035

Abstract (EN): Secondary phases such as Laves and carbides are formed during the final stages of solidification of the nickel based superalloy Inconel 625 coatings deposited during the gas tungsten arc welding (GTAW) cold wire process. However, when aged at high temperatures, other phases can precipitate in the microstructure, like the gamma '' and delta phases. The aim of this work was to evaluate the different phases formed during thermal aging of the as-welded material through ultrasound inspection, as well as the influence of background echo and backscattered ultrasound signals on the computational classification of the microstructures involved. The experimental conditions employed an aging temperature of 650 degrees C for 10, 100 and 200 h. The ultrasound signals were acquired using transducers with frequencies of 4 and 5 MHz and then processed to determine the ultrasound velocity and attenuation, as well as to study the background echo and backscattered signals produced by wave propagation. Both signal types were used to study the effectiveness and speed for classifying the secondary phases, using detrended fluctuation analysis and the Hurst method in the signal pre-processing and the Karhunen-Loeve Transform in the classification of the microstructures. The ultrasound signals and the signal processing tools used were considered sufficiently sensitive, fast and accurate in the detection and classification of the microstructures in the as-welded and aged Inconel 625 alloy using this nondestructive technique.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11