Sensitization to Corrosion as Initiator of Fatigue Fracture in Compressor Blades

• Main Authors: Vladimír CIHAL, Marie BLAHETOVÁ, Eva KALABISOVA, Zdena KRHUTOVÁ, Stanislav LASEK, Jiri MIKA, Libor TUREK
• Format: Article
• Language: English
• Published: VSB-Technical University of Ostrava 2011-06-01
• Series: Transactions of the VSB : Technical University of Ostrava
• Subjects: stainless steel; corrosion; ERP
• Online Access: http://transactions.fs.vsb.cz/2011-1/1836_Cihal.pdf

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.