Study of annealing temperature effect on stress-corrosion cracking of aluminum brass heat-exchangers tubes by microdiffraction experiments

Laboratory investigations were carried out on C68700 copper alloy heat-exchangers tubes to study the effect of stress relieving annealing at different temperature and time to prevent SCC phenomena. The analysis includes metallographic characterizations, mercurous nitrate tests and residual stress measurements by X-ray microdiffraction. A significant decrease of residual stresses was registered after standard annealing at 250 °C; similar results were obtained at 200 °C for longer time demonstrating the opportunity to achieve a good stress-relief also at lower temperature.