Investigating the Cyclic Oxidation and Hot Corrosion of Nanostructured CoNiCrAlYSi Coatings Applied by HVOF Process

In this research, cyclic oxidation and hot corrosion behavior of nanostructure CoNiCrAlYSi coatings, deposited by HVOF thermal spray process, have been investigated. To achieve nanosized particles, the initial CoNiCrAlYSi powder was cryomilled and then HVOF sprayed to form a nanostructure coating. The coating’s performance has been evaluated via cyclic oxidation and hot corrosion tests. Microstructure changes and phase analysis of the coatings during tests have been studied. The coatings endured on the substrate for 115 cycles and 700 hours during cyclic oxidation and hot corrosion tests, respectively. The increased lifetime of nanostructure coatings with respect to conventional coatings is attributed to some α-Al2O3 particles dispersed in the structure, created by cryomilling, and high-diffusivity paths as a result of nanocrystallization, which favors the formation of a continuous and protective α-Al2O3 barrier layer on the top of the coating.