HITS: High insulation thermal barrier coating systems

• Unité de recherche: PCRD EU
• Numéro de projet: 96.0300
• Titre du projet anglais: HITS: High insulation thermal barrier coating systems

Mots-clé (Anglais)

TBCs; thermal barrier coatings; plasma spraying; EB-PVD; zirconia; zircon; new compositions; new microstructures; low thermal conductivity

Autre Numéro de projet (Anglais)

EU project number: BRPR-CT96-0338

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)

Coordinator: SNECMA (F)

Résumé des résultats (Abstract) (Anglais)

The HITS project's goals were to develop new composition and microstructure thermal barrier coatings with significantly improved performance for aerospace and diesel engine applications. By the begginning of the year 2002, the scientific development had already been undertaken and the remaining tasks were focussed on generating performance indications in real in-situ engine tests. Sulzer Innotec's tasks focussed on the evaluation of TBC coatings on valve faces in large ships diesel engines. Due to earlier evidence from the development programme of corrosion susceptibility in the severe two stroke service regime, the initial target of applying the TBCs in two stroke diesel engines was ammended to application in a four-stroke environment. The results of in-situ engine tests on coated valves showed that the TBC systems developed could survive real service environments and therefore hav ethe potential to make a significant impact on the fuel efficiency and operational ecconomy of large diesel engines.

Engine tests on coated valves
The components chosen for coating were standard valves; two in a stationary engine at ETH Zürich (S20) and two each in on-board Sulzer design 4-stroke diesel engines (12ZAV40 and 6ZAL40). No special design of components was required. A set of four outlet valves was coated for both test engines; in the stationary S20 engine at ETH Zürich, Switzerland, and the ZA 40 engine on board of the Kronprins Harald, Color Line, Oslo, Norway. Two valves of each set were coated with the ZS-R coating and the P-YSZ coating respectively. QIA analysis revealed results being consistent with the P-YSZ reference such that these components could be released for installation in the engines.
Details of the coating evaluations after service are to be found in the SIT reports: SWA TM01 0862/PR, SWA TM01 0734/PR and SWA TM02 0119/PR. Valves tested in the S20 engine at the ETH saw about 480 hrs of running time. Valves tested on the Kronprins Harald experienced about 3000 to 3500 hrs running time.
Analysis of the coatings after service clearly confirms that both coatings are capable of surviving extended periods in service in a real engine. As the valves tested on the Kronprins Harald were exposed to the more severe conditions, this evaluation concentrates on the condition and characteristics of these tests.
The partially stabilized zirconia coatings tried on the Kronprins Harald appear to have been partially consumed in operation. The zircon coating tried on the Kronprins Harald also survived the service trial more or less intact. In general, it may be concluded that both the selected coatings performed well in the engine tests. The ZS-R coating in particular appeared to be the more promising TBC materials for diesel applications in which both thermal insulation and corrosion protection are required.

Conclusions:
Ø Concerning Diesel applications, compositional changes have shown to be a very effective means of lowering the thermal conductivity of coatings. The mere fact of replacing zirconia coatings by zircon (zirconium silicate) ones allowed to obtain values of conductivity as low as 0.4 W/mK.
Ø As-coated Diesel engine valves have been mounted and tested on 2 different engines (a stationary diesel engine for building heat supply S20 and a ship diesel engine ZA40 that has been operated on a real cruiser between Oslo and Kiel). Both the selected coatings performed well in the engine tests.

Exploitation:
The surface attack through corrodants is considered as the dominant factor for component life in heavy duty fuel oil fired two stroke engines. The objective to develop a protective surface modification for zirconia or zircon based plasma sprayed coatings was not achieved for this specific application. As a consequence, exploitation is directed towards four stroke engines being fired with cleaner fuel.
In consequence of the successful engine tests on a Color-Line vessel, contacts are being established to extend the development and application of the Zircon TBC coatings in 4-stroke engines.
The exceptionally low thermal conductivity of the Dy-Zirconia has led to great commercial interest in this new material. Sulzer has begun a process to speed up the full commercial exploitation of this material.

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: 96.0300