Effect of Corrosion-Resistant Coatings on Fatigue Properties of Gas Turbine Blade Materials

Abstract

Isotherma］low − cycle fatigue tests and thermal − mechallical fatigue tests with linear ollt elphase cyclcs wcrc carried 〔 〕ut Llsing cylindrical specimens made of Ni base superalloy and coated 、 vith several kinds 〔 ｝ f c 〔 〕 rrosion re ＄亙 stan し coatings ． Irl some tests， fatigue luading was iIlterr し ipted severaI times and coating cracks were obserlved by lneans 〔 ｝f replica technique 、 As a resu ］ t ， threc typcs of coating cracks were observed ， namely ， rnultipie parallel l 〔)ng cracks ， muitiple parallel sh 〔 ， rt cracks and lloll − paral ［ el cracks 、 Pvlultiple parallel ユ orlg cracks are caused from ユ ack of ductility of coa 亡 ［ ng rnaterials ． This し ｝pe of coating cracks l項 tiate in un eurly stuge of fatigue l 〔 〕ading and has a strung effcct to reduce fatigue Iife ． Mul し iple para1lel short cracks are caused by fatigue〔 〕f coating layer 、 These cracks propagate into the substrate bcfore cracks initiate in the substrute ar ユ d reduce fatigue ユ ife 〔＞ f the coated specimen ． No 冂 一 parallel coating crac1 くs arc causcd by pr 研 〕agation c〕f cracks initiated in the substrate and have litt 且 e effect to reduce fatigue Iife，