Elastic-plastic fracture mechanics approach for stress corrosion cracking of nickel aluminium bronze under ammonia-containing artificial seawater

With the growth of urbanization and industries, the seawater near coastal areas has become polluted, and the nickel aluminium bronze components around coastal areas are affected by ammonia-containing seawater. Unfortunately, the influence of the ammonia concentration in seawater on the stress corrosion cracking of thin nickel aluminium bronze components with large plastic zones at the defects has not been evaluated before. In the present work, stress corrosion cracking experiments on nickel aluminium bronze components under artificial seawater and ammonia-containing artificial seawater were conducted using a four-point bending technique. The elastic-plastic fracture mechanics parameter (J-integral) was evaluated using finite element analysis. The J-integral successfully characterized the crack growth rate under the present corrosive environments. Stress corrosion cracking was possible under both artificial seawater and ammonia-containing artificial seawater. The threshold J-integral for susceptibility to stress corrosion cracking (J(SCC)) and fracture toughness (J(C)) was the highest for stress corrosion cracking under artificial seawater and decreased as the amount of ammonium hydroxide added to the artificial seawater increased.