Zcitlivění ke korozi jako iniciátor únavového lomu lopatek kompresoru

Abstract Certain failures of stainless steels interpreted purely in terms of fracture mechanisms may in fact be closely associated with previous damage caused by localized corrosion. The closeness of the link between fatigue and corrosion is documented by the case history of compressor blades made of grade 14Cr17Ni2 (X14CrNi17-2) stainless steel. Fatigue fracturing observed in areas near the blade root tended to follow intergranular pathways, indicating that some additional mechanism other than fatigue might be involved. This suspicion was confirmed by electrochemical potentiokinetic reactivation (EPR) measurements in situ, which revealed sensitization to intergranular corrosion. It has been found that at the transition between the blade root and the blade proper the surfaces had been ground and polished too vigorously, heating the subcutaneous layers to within the danger zone of 400-600°C. Preferential integranular attack in these locations was the initiation mechanism that provoked a subsequent failure of the blades by fatigue fracture.Určité poruchy korozivzdorných ocelí zdůvodňované čistě ve smyslu lomové mechaniky mohou být ve skutečnosti úzce spojeny s dřívějším poškozením způsobeným místní korozí. Souvislost mezi únavou a korozí představuje případ lopatek kompresoru vyrobených z korozivzdorné oceli typu 14Cr17Ni2. Únavové poškození (praskání) pozorované v oblastech blízko paty lopatky má tendenci sledovat mezikrystalovou cestu. To naznačuje, že přichází v úvahu i jiný mechanismus vzniku trhlin, než je únava materiálu. Toto podezření bylo potvrzeno elektrochemickým potenciokinetickým reaktivačním (EPR) měřením „in situ―, které odhalilo zcitlivění k mezikrystalové korozi. Bylo zjištěno, že v přechodu mezi patou lopatky a ostatními povrchy byla broušena a leštěna příliš razantně a došlo k ohřátí povrchových vrstev v rozsahu teplot 400-600°C. Přednostní mezikrystalové napadení v těchto místech bylo iniciačním mechanizmem pro vyvolání následujícího poškození lopatek únavovým lomem

Characterization of hydroxyapatite layer on AISI 316L stainless steel.

Bioactive coatings can be divided into two main groups - organic and inorganic coatings. Hydroxyapatite (HA) is well known as one of inorganic part of mammal's bone structure and is highly recommended for use in implantology. This paper is mainly focused on characterization of hydroxyapatite particles electrochemically deposited from water solution of Ca(NO3)2 and NH4H2PO4 on surface of AISI 316L (1.4404) stainless steel with different roughness profiles and surface treatment. The effect of surface roughness itself is discussed as well as heat treatment (400 {deg}C) of samples after coating deposition. Electrodeposition of HA was carried out at cycling of potential values of -2.0 V for 2 s and 0 V (NHE) for 1 s; 200 cycles was used for this study. Electrochemical properties of such treated samples were characterized using voltammetry and EIS methods. It was found, that time of deposition significantly changes electrochemical parameters of equivalent el. circuit used for closer characterization of coating properties but only marginally affects corrosion properties like open circuit potential (OCP), corrosion potential (Ecorr) or potential of passive layer breakdown (Ebreak). Pull-off test also proved significant correlation between surface roughness, heat treatment and adhesion of deposited coatings

Influence of thermal treatment on structure and corrosion properties of high manganese triplex steels

In this paper corrosion properties of X70MnAl28-9 TRIPLEX steel were tested after hot rolling and subsequent aging at 500 °C for 6, 30 and 60 min. and at 600 °C for the same times. For comparison related steels(X100MnAl28-12, X70Mn22, C20) were also used. The microstructure wascharacterized by light microscopy, SEM, energy disperse Xray microanalysis. The corrosion behaviour of steels wasexamined by light and scanning electron microscopy, electrochemical techniques (potenciodynamic polarization method, linear polarization, using NaCl and H2SO4 water solutions), salt spray test and gravimetric method. Aging has relatively small infl uence on corrosion resistance of X70MnAl28-9 steel. The localized corrosion in relation to structure and phases is discussed and compared in terms of dissolution, pitting and changes inchemical composition.Web of Science52444444

Bodová koroze vysokolegovaných korozivzdorných ocelí

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta metalurgie a materiálového inženýrstv

Lokální koroze vybraných kovových biomateriálů

Import 09/08/2006PrezenčníNeuveden

Elektrokemijsko ispitivanje stabilnosti pasivnog stanja i korozijske otpornosti supermartenzitnog nehrdajućeg čelika

On low interstitial - supermartensitic stainless steels (X1CrNiMo 12-5-1, X2CrNiMo 13-6-2, X1CrNiMo 12-6-2) the electrochemical potentiodynamic polarization tests were carried out and the passive state stability and localized corrosion resistance were compared and evaluated. The effect of quenching and tempering as well as the changes in microstructure on polarisation curves and corrosion properties at room temperature were established. Small differences in chemical composition of steels were also registered on their corrosion parameters changes and resistance.Rad prikazuje usporedbu i procjenu stabilnosti pasivnog stanja i lokalnu otpornost koroziji temeljem ispitivanja elektrokemijske potenciodinamičke polarizacije nisko-intersticijskih supermartenzitnih nehrdajućih čelika (X1CrNiMo 12-5-1, X2CrNiMo 13-6-2, X1CrNiMo 12-6-2). Utvrdeni su utjecaj poboljšavanja čelika i mikrostrukturne promjene na polarizacijskim krivuljama uzoraka te korozijska svojstva pri sobnoj temperaturi. Uočena je i povezanost malih odstupanja kemijskog sastava čelika s promjenom korozijskih parametera i korozijskom otpornošću