Investigation of Blanching behavior of Cu-Ag-Zr alloy using oxidation-reduction cycles

Blanching of copper alloys is a major life-limiting degradation mechanism in rocket combustion chambers. Understanding of this mechanism is key to further improvement of rocket engine performance, so to gain further insight into the mechanism oxidationreduction cycles with a variation of temperature, amount of cycles and reduction atmosphere composition have been used to duplicate the blanching mechanism on sample scale. As part of the evaluation the sample weight and the roughness have been measured in the initial state as well as after testing. Furthermore, scanning electron microscope (SEM) investigations have been conducted to distinguish whether sponge-like blanching structures formed during testing. The roughness measurements showed a smoothing of the surface up to about 600°C, with a maximum at about 500°C. Above these temperatures the roughness increased rapidly. The SEM investigation proved to deliver sponge-like blanching structures, also with a strong dependence on temperature. The experiments proved to give trends on the influence of the individual parameters. Temperature was found to be the principal influencing factor, followed by the duration (amount of oxidation-reduction cycles). The composition of the reduction atmosphere was found to play only a supporting role. The results obtained in this study will be the baseline for further investigations in the newly developed Airbus Group Innovations ERBURIG H test facility.