Abstract
Metallographic investigations of worn abradable coatings have been carried out to identify and characterize the main wear mechanisms occuring in turbomachine seals. The following mechanisms have been found: cutting, smearing, adhesive transfer, crushing, melting and tribo-oxidation. Three other mechanisms occur without blade-seal interaction: erosion, corrosion and high-temperature oxidation. Using the data from these investigations as a reference, rub tests have been conducted on a specially designed high-speed—high-temperature rig. The many correlations obtained between test values and wear mechanisms allow the generation of ‘wear mechanism maps’ for coatings of the AlSi-plastic family. Mechanism orientated model tests are needed to understand the correlations between structural parameters and coating behaviour during blade-coating interactions. Wear mechanism maps will help modelling coating systems to be able to withstand severe service conditions. Avoiding the onset of adhesive or melting wear and simultaneously favouring cutting wear produces better abradable seals which will help improve both the operational safety and the economy of modern turbomachines.
Highlights
Modern turbomachines need very small clearances between rotating components and the stator case in order to minimize gap losses and so increase efficiency
Different types of abradable seals are deposited on the stator case to cope with rotor misalignment, thermal and centrifugal dilatations, and unbalanced parts
The primary requirement of abradable seals is to allow for wear without damage to the blade tip
Summary
Metallographic investigations of worn abradable coatings have been carried out to identify and characterize the main wear mechanisms occurring in turbomachine seals. The following mechanisms have been found: cutting, smearing, adhesive transfer, crushing, melting and tribo-oxidation. Three other mechanisms occur without blade-seal interaction: erosion, corrosion and high-temperature oxidation. The many correlations obtained between test values and wear mechanisms allow the generation of 'wear mechanism maps' for coatings of the A1Si-plastic family. Mechanism orientated model tests are needed to understand the correlations between structural parameters and coating behaviour during blade-coating interactions. Wear mechanism maps will help modelling coating systems to be able to withstand severe service conditions. Avoiding the onset of adhesive or melting wear and simultaneously favouring cutting wear produces better abradable seals which will help improve both the operational safety and the economy of modern turbomachines
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
