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High performance environmental barrier coatings, Part II_ Active

Available online at http://www.wendangku.net/doc/68d67b59af45b307e9719733.html Journal of the European Ceramic Society31(2011)

High performance environmental barrier coatings, Part II_ Active

3011–3020

High performance environmental barrier coatings,Part II:Active?ller

loaded SiOC system for superalloys

Kaishi Wang a,Martin Günthner b,Günter Motz b,Rajendra K.Bordia a,?

a University of Washington,Department of Materials Science and Engineering,Seattle,WA98195-2120,USA

b University of Bayreuth,Cerami

c Materials Engineering(CME),D-95440Bayreuth,Germany

Received2March2011;received in revised form23May2011;accepted31May2011

Available online13July2011

Abstract

Polymer derived ceramic(PDC)matrix composite coatings are a promising candidate to be used as alternative environmental barrier coatings, such as in oxidation protection.This paper reports the processing of three PDC coating systems on a superalloy substrate,Inconel617,using a simple dip coating method.The performance of SiON coating,particle?lled SiOC coating,and their combined coating system is evaluated by long time static oxidation testing at800?C for100–200h.Two key parameters have been analyzed:the weight gain of the coating samples and the thickness of the thermally grown oxide(TGO)layer at the ceramic–metal interface.Results show that all three coating systems are able to signi?cantly reduce the weight gain of metal substrates due to oxidation.However,the SiON bond coat+particle?lled SiOC top coat double-layer coating system is most effective in maintaining the integrity of the substrate in the investigated200h.Based on the kinetics of oxidation,likely rate controlling steps are identi?ed.

?2011Elsevier Ltd.All rights reserved.

Keywords:Polymer derived ceramics;Composites;Interfaces;Structural applications;Failure analysis

1.Introduction

Ceramic coatings play an important role in providing struc-tural or environmental protection and functionality to a system. Commercially,expensive vapour phase techniques,like PVD and CVD,are used to deposit single or multi-elemental ceramic materials,for instance,those used in gas turbines.In contrast, a large number of preceramic polymers are liquid or soluble so that low-cost alternatives such as dip-coating,spray-coating and spin-coating can be utilized to deposit polymers or their solu-tions onto substrates,which can then be converted to ceramic coating materials.And since the polymer derived ceramic(PDC) approach is a liquid based technique,it is non-line of sight and able to coat complex shapes.

DOI of original article:10.1016/j.jeurceramsoc.2011.05.018.

?Corresponding author.Tel.:+12066858158;fax:+12065433100.

E-mail addresses:kshwang@http://www.wendangku.net/doc/68d67b59af45b307e9719733.html(K.Wang),

martin.guenthner@uni-bayreuth.de(M.Günthner),

guenter.motz@uni-bayreuth.de(G.Motz),

bordia@http://www.wendangku.net/doc/68d67b59af45b307e9719733.html(R.K.Bordia).

SiCN ceramic coatings have been produced in multiple ways. Zeigmeister1used spray-coating method to make50?m-thick SiCN ceramic coating on C/C/SiC substrate;a dense and nearly crack-free coating is achieved by repeating the procedure4 times.SiCN coatings have been proposed for wear,erosion or corrosion protection applications2as well as micro-electronic and optoelectronic devices.3Using a specially tailored ABSE polycarbosilazane solution as precursor for dip-and spray-coating techniques,Motz et al.4coated complex-shaped samples with a ceramic-like coating(at higher temperatures)that has good corrosion and thermal stabilities;moreover,the high?ex-ibility of ABSE?lm also allows the coating of?exible metal foils.SiCN membranes(200–500nm thick)can be spin-coated onto a porous Si3N4substrate for hot gas separation applications due to their high temperature stability.5Iwamoto et al.6reported such a microporous amorphous membrane that exhibits hydro-gen gas permeance of1.3×10?8mol/m2s Pa at573K and the selectivity ratio of H2/N2at141.

SiOC ceramic coatings are attractive because they can be used as thermal or environmental barrier coatings against harsh environments at elevated temperatures.Fukushima et al.7used transition metals as catalyst and alkoxysilane as precursor to

0955-2219/$–see front matter?2011Elsevier Ltd.All rights reserved. doi:10.1016/j.jeurceramsoc.2011.05.047

High performance environmental barrier coatings, Part II_ Active