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Mechanisms for corrosion fatigue crack propagation
Author(s) -
SHIPILOV S. A.
Publication year - 2002
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1046/j.1460-2695.2002.00447.x
Subject(s) - materials science , corrosion , cathodic protection , polarization (electrochemistry) , paris' law , corrosion fatigue , metallurgy , crack closure , stress corrosion cracking , growth rate , composite material , fracture mechanics , anode , electrode , chemistry , geometry , mathematics
The corrosion fatigue crack growth (FCG) behaviour, the effect of applied potential on corrosion FCG rates, and the fracture surfaces were studied for high‐strength low‐alloy steels, titanium alloys, and magnesium alloys. During investigation of the effect of applied potential on corrosion FCG rates, polarization was switched on for a time period in which it was possible to register the change in the crack growth rate corresponding to the open‐circuit potential and to measure the crack growth rate under polarization. Due to the higher resolution of the crack extension measurement technique, the time rarely exceeded 300 s. This approach made possible the observation of a non‐single mode effect of cathodic polarization on corrosion FCG rates. Cathodic polarization accelerated crack growth when the maximum stress intensity ( K max ) exceeded a certain well‐defined critical value characteristic for a given material‐solution combination. When K max was lower than the critical value, the same cathodic polarization, with all other conditions (specimen, solution, pH, loading frequency, stress ratio, temperature, etc.) being equal, retarded or had no influence on crack growth. The results and fractographic observations suggested that the acceleration in crack growth under cathodic polarization was due to hydrogen‐induced cracking (HIC). Therefore, critical values of K max , as well as the stress intensity range (Δ K ) were regarded as corresponding to the onset of corrosion FCG according to the HIC mechanism and designated as K HIC and Δ K HIC . HIC was the main mechanism of corrosion FCG at K max > K HIC (Δ K > Δ K HIC ). For most of the material‐solution combinations investigated, stress‐assisted dissolution played a dominant role in the corrosion fatigue crack propagation at K max < K HIC (Δ K < Δ K HIC ).