Stress Corrosion Cracking Susceptibility Of Alloy Research Articles

The effect of testing conditions on stress corrosion cracking of biodegradable magnesium alloy ZK60

The effect of the chemical composition, temperature, circulation and pH of the simulated body fluid (SBF) on the corrosion and stress corrosion cracking (SCC) susceptibility of the alloy ZK60 was studied through the immersion and slow-strain rate tensile (SSRT) testing respectively. It is found that both the corrosion and SCC susceptibility of the alloy is significantly affected by chemical composition and adjustment of pH level of SBF, while the temperature and circulation of the SBF exert a minor effect on these characteristics. The pH adjustment of 0.9 % NaCl solution to 7 ± 0.2 was done automatically and continuously during the SSRT testing by refreshment of the SBF. The control over pH decreased the corrosion rate and increased the SCC susceptibility of the ZK60 alloy. It is established that, in the considered SBFs (0.9 % NaCl, Ringer’s and Hank’s solutions), the alloy ZK60 possesses the highest SCC susceptibility and the least corrosion rate in Hank’s solution, while in Ringer’s solution, the SCC susceptibility and corrosion resistance are lowest. It is concluded that the experimental factors considered in the present study have to be accounted for in the reliable assessment of the corrosion and SCC resistance of the biomedical Mg alloys.

Stress Corrosion Cracking Behavior of Alloy 182 Weld in Pressurized Water Reactor Primary Water Environment at 325ºC

Abstract The weld used to connect two different metals is known as a dissimilar metal weld (DMW). In nuclear power plants, this weld is used to join stainless steel to low-alloy steel components in the nuclear pressurized water reactor (PWR). The most common weld metal is Alloy 182 (UNS W86182). Originally selected for its high corrosion resistance, it exhibited, after a long operation period, susceptibility to stress corrosion cracking (SCC) in PWR. The goal of this work was to study the electrochemical corrosion behavior and SCC susceptibility of Alloy 182 weld in PWR primary water containing 25 cm3 and 50 cm3 H2/kg H2O at standard temperature and pressure (STP). For this purpose, slow strain rate tensile (SSRT) tests and potentiodynamic polarization measurements were carried out. Scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS) was used to evaluate fracture morphology and determine the oxide layer chemical composition and morphology. The results indicated that at 325°C Alloy 182 weld is more susceptible to SCC at 25 cm3 (STP) H2/kg H2O and the increase of dissolved hydrogen decreased the crystal size of the oxide layer.