Cascade Testing of Ceramic Vanes for Industrial Gas Turbines

Abstract

The development of uncooled ceramic vanes for a 20MW class gas turbine with the firing temperature of 1300°C is progressing.The 1st stage ceramic vanes were made of sintered SiC or sintered Si3N4 , and the 2nd stage ceramic vanes were made of sintered Si 3N 4 . These vanes were tested by means of hot and high pressure cascade testing simulating actual gas turbines operation.After minor modifications, we have succeeded in developing sound ceramic vanes which are durable against high thermal stress which occurs during the transient of trip (emergency shutdowns or fuel tripouts), and obtained great results for the practical application.In this paper, details of the ceramic vanes' structure and cascade testing are described and the results of the tests are discussed.

Dense and near-net-shape fabrication of Si3N4 ceramics

“…These techniques can be summarized: i) Reaction Bonding Silicon Nitride (RBSN), ii) Hot Pressing Silicon Nitride (HPSN), iii) Sintering Silicon Nitride (SSN), iv) Sintering Reaction Bonding Silicon Nitride (SRBSN), v) Hot Isostatic Pressing Silicon Nitride (HIPSN), vi) Hot Isostatic Pressing Reaction Bonding Silicon Nitride (HIPRBSN), vii) Hot Isostatic Pressing Sintered Silicon Nitride (HIPSSN) and viii) Hot Isostatic Pressing Sintered Reaction Bonded Silicon Nitride (HIPSRBSN) [20,[22][23][24][25][26][27][28][29][30][31][32][33][34]. It is very difficult to produce pure dense silicon nitride ceramics by means of conventional sintering (simple heating of powder compacts) due to the high degree of covalent bonding between silicon and nitrogen [35].…”

“…The sintering of silicon nitride is very difficult because of the low self-diffusivity of this covalent material [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Doping pure Si 3 N 4 with of some oxides provides the formation of intergranular liquid phase which aids the further densification of the silicon nitride during different sintering routes [3][4][5][6][7][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. These oxides, however, remain as grain boundary glassy phase, which deteriorate the high temperature properties of the ceramics such as creep and high temperature strength [17,32,33].…”