Enhanced high-temperature oxidation resistance of TP347H supercritical boiler steel via vacuum cladding HEA coating at 800 ° C

Abstract

This study investigates the improvement of high-temperature oxidation resistance in supercritical boiler steels at 800 degrees C through vacuum cladding NiCoFeCrMoSi1.2B1.1 HEA coatings on TP347H steels. The findings demonstrate that the HEA coating exhibited a strong metallurgical connection with the substrate and an FCC + sigma eutectic structure. With an average oxidation gain of only 12.8 % over 288 h, the HEA coating's oxidation rate constant was far lower than that of TP347H steel. The HEA coating showed a low-speed homogenous oxidation behavior with Cr2O3 as the primary oxide and a trace quantity of spinel, while the oxide of TP347 steel was Fe2O3. The oxide layer of the TP347H steel thickened at a rate 71.1 times faster than that of the HEA coating, suggesting that the former oxidized more quickly than the latter. The persistent interaction of loosely organized Fe2O3 oxides and metal shedding are the primary causes of TP347H steel's low oxidation resistance. The excellent high- temperature oxidation resistance of the HEA coatings is a result of the ongoing development and protective action of Cr2O3 dense oxide. The main high temperature diffusion mechanism is the inward diffusion of external O element and the quick outward diffusion of Cr element on the surface of the HEA coating. For the development of high-performance supercritical composite boiler steel, this work offers solid experimental and data support, and it has significant reference value.