Evaluation of NiCrAl foil for a concentrated solar power application

A NiCrA1-type foil (alloy 214) was selected for evaluation for heat exchanger applications for a concentrated solar power (CSP) system. Due to the formation of a protective alumina surface oxide, this class of alloys can operate at higher temperatures than conventional stainless steels or even Ni-base alloys, such as alloy 625. Laboratory testing is being conducted at 1000° and 1050°C in dry air using 10 h thermal cycles in order to simulate the CSP duty cycle at a high temperature to accelerate the degradation process. Mass change data showed indications of degradation of the foils with exposures up to 8,000 h. Foil specimens also were stopped after 2,400 h to measure the loss of A1 in the foil as a method to predict lifetime. Previous lifetime modeling results for 1h cycles in air with 10%H₂O provided an initial basis to predict lifetime for this material to > 100,000 h operating times as a function of foil thickness and exposure temperature for this application.