Thermal cycling and isothermal tests on black-coated specimens

Thermal cycling and isothermal tests were performed on AISI 316 L(N) austenitic steel with different types of black coating. The adhesion and the fatigue life of the coatings, as well as the fatigue of the base material were investigated. The tests were performed in different test rigs, using tubes and circular discs. The discs were subjected to cyclic heating on the coated side, using an Ar + He + 1% H2 flame in a plasma spray facility. The tubes, coated on the outside, were induction heated. The temperature ranges typical for first wall applications were about 150–430 °C on the discs and 80–435 °C for the tubes. Isothermal strain-controlled uniaxial tests on coated tubes have been carried out as a base comparison for the thermal cycling experiments. In this report, the test rigs are described and the results of the tests are presented. For the tubes, the adhesion of the coatings up to high loadings was surprisingly good. Likewise, no accelerated fatigue of the base material was observed to be caused by the coatings. For the discs, nearly all the coatings survived 10 000 load cycles.