ABRATIP: Advanced abradables and tip coatings for gas turbines

• Unité de recherche: PCRD EU
• Numéro de projet: 95.0190
• Titre du projet anglais: ABRATIP: Advanced abradables and tip coatings for gas turbines

Mots-clé (Anglais)

Abradable coating; blade tipping; ceramic; metallic

Autre Numéro de projet (Anglais)

EU project number: BRPR-CT96-0187

Programme de recherche (Anglais)

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

Description succincte (Anglais)

See abstract

Partenaires et organisations internationales (Anglais)

Turbomeca (F), A.T. Poeton (UK), ECL (F), BMW Rolls-Royce (D), BAM (D), MTU (D), Snecma (F), Techspace Aero(B)

Résumé des résultats (Abstract) (Anglais)

In order to improve efficiency of gas turbines (i.e. areo engines as well as land based gas turbines), the gap between the rotating turbine blades and stator parts must be controlled. Any increase in the gap results in power loss. The aim of this programme is to develop high temperature metallic as well as ceramic abradable coatings and suitable abrasive blade tip materials in order to maintain control over the interaction of the two parts. The abrasive tip on the turbine blade must be able to cut into the abradable in an operating temperature range of 1000 - 1200 °C being worn. The developed materials will have a defined processing technique which takes into account cost factors and ease of manufacture.
Sulzer's involvement in the project as task leader as well as work package leader is as follows;
· Development of tip coating materials
· Development of a tip coating process
· Development of abradable coatings
· Laboratory based wear characterisation of the abradable coating and blade tip pair

The forth year of the project was prolonged by 6 months due to a delay in the overall program.
The development of an encapsulated SiC grit material was continued although the first results achieved on abrasive blade tips which were produced using the new grit material in combination with laser cladding, a process developed by Sulzer Innotec were not very encouraging. The deposition of AlN diffusion barrier coating as an encapsulation around the sharp-edged SiC grains was very irregular and as a result of the coating process it was very thin along the edges and at the corners. In addition the adhesion to the AlN to the SiC was not good and spallation of the coating could be observed. The difference in coating thickness lead to high residual stresses in the coating and during the laser welding process a large number of cracks occurred.
The problems were mainly attributed to the sharp-edged shape of the SiC particles. As a result Sulzer tried to find a supplier of round shaped SiC particles, which could finally be identified. In the meantime the particles have been coated with AlN, the coating thickness is very uniform and no spallation could be observed so far. No tests have been carried out so far with laser welding of the new rounded SiC particles.
Additional rub in tests had been carried out by Sulzer Innotec on their test rig in Winterhtur. The purpose of the tests was to check the robustness of the newly developed AE7460 with regard to the effect of variations in spray parameters. The results showed, that significant changes in the spray parameters did not affect the hardness of the coatings, which also resulted in similar behavior in abradability. This confirms, that the manufacturing process is very robust and allows for variations in processing parameters without the risk to obtain different properties of the final coating.
Three final abradability tests were carried out middle of December 2000 in order to create some data points where data was missing of to complete the overall picture of modified and heat treated SM2043 coatings.

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: 95.0190