Luna has developed an in situ measurement system that can be used to characterize environment assisted cracking and premature failure of alloys.

Environment assisted cracking sensor and fracture samples.

Environment assisted cracking of high strength alloys is a significant technical and safety concern for civil and defense applications. In particular, structures that are cathodically protected may suffer from environment assisted cracking after prolonged exposure due to hydrogen embrittlement.  As application requirements become more severe, there is a growing need to use advanced high strength alloys; however, there has been reluctance to use these materials given the associated risks of hydrogen embrittlement and subsequent cracking at cathodic potentials.  Measurement of environment assisted cracking using short term tests is particularly difficult since significant variability in crack initiation can occur and long times may be required to obtain crack growth measurements. 

 

Luna has developed an in situ measurement system that overcomes these issues and can be used in service settings to characterize environment assisted cracking and premature failure of alloys.  The system is compact and rugged to enable distributed measurements over a structure.  In addition to monitoring crack velocity in a surrogate sample, the system tracks electrochemical reference potential and ambient temperature as secondary indicators of environmental severity. The patent pending system has been used to measure environment assisted cracking of a variety of alloys in natural seawater tanks, and crack velocities well below nanometers per second can be rapidly resolved in a matter of hours. A low power standalone (battery powered) sensor variant is available when real time data acquisition is not required.

 

Multichannel system and environment assisted cracking sensors for immersion use in seawater

 

  

Crack velocity measurements for 17-4 PH steel and K-500 nickel copper alloy obtained with the environment assisted cracking measurement system.