BI-METAL: Mechanics of bi-metallic discs

• Unité de recherche: PCRD EU
• Numéro de projet: 97.0403
• Titre du projet anglais: BI-METAL: Mechanics of bi-metallic discs

Mots-clé (Anglais)

HIgh temperature; bimetallic joint; Udimet 720; single crystal M2C; nondestructive evaluation

Autre Numéro de projet (Anglais)

EU project number: $BE 97-4296

Programme de recherche (Anglais)

EU-programme: 4. Frame Research Programme - 2.1 Industrial and materials technologies

Description succincte (Anglais)

See abstract

Autres indications (Anglais)

Full name of research-institution/enterprise:
Eidg. Materialprüfungs- und Forschungsanstalt EMPA
Leiter ZfP Sonderverfahren

Partenaires et organisations internationales (Anglais)

Coordinator: CEA/CEREM (F)

Résumé des résultats (Abstract) (Anglais)

The main objectives of this project was to develop a methodology to assess the lifetime of a high temperature bimetallic component like a gas turbine disc. The work comprises manufacturing and testing, development of mechanical models to describe both behaviour and damage and finally a validation of the proposed methdology. Two types of bimetallic joints were studied:Coarse grain Unimet 720 (cast and wrought) to fine grain Udimet 720 (powder material) and single crystal MC2 to fine grain Udimet 720. Compared to standard mono material, the bimetallic material shall have better mechanical properties: the coarse grain material or single crystal material being a high creep resistant material is devoted to the rim of the gas turbine disc. The fine grain material (U720 powder material) being a high strength alloy is devoted to the hub.
Nondestructive evaluation methods have been developed by EMPA to inspect the interface zone of the bonded bimetallic joint. Reference bimetallic samples for nondestructive evaluation with intended artificial planar flaws in the joint were manufactured. The artificial flaws were introduced by inserting small aluminia particle in the interface before joining the two materials by HIP (hot isostatic pressure) diffusion bonding process. The reference bimetallic sample underwent X-ray (computer tomography) and ultrasonic inspection to verify the size of the planar interfacial flaws. Some differences were observed between the X-ray measured size and the ultrasonic measured size. But all measured flaw sizes were within the intended diameter range.
Afterwards ultrasonic inspection (using immersion technique and the pulse - echo method) was performed to develop a suitable inspection technique which is able to detect small flaws in the bimetallic joint at increased material distances. The best nondestructive testing results were achieved with spherical focussed ultrasonic transducers with nominal frequency of 5 and 10 Mhz. From the results gained at the reference samples, it can be concluded, that the applied ultrasonic inspection techniques are capable to detect small planar flaws at the bimetallic bonding interface zone.

Références bases de données (Anglais)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0403