Evolution in microstructure and oxidation behaviors of the laser cladding C22 coatings with the Si addition concentrations

Abstract

C22 coatings with different concentrations of Si (0 wt%, 1 wt%, 2 wt% and 3 wt%) were prepared on TP347H by laser cladding. The effect of Si on the microstructure evolution, phase constitution and high temperature oxidation behaviors were systematically investigated. The results show that the oxidation kinetics of coatings follow a parabolic law at different temperatures. Double-layer structure of oxidation products were observed, including NiO, Cr2O3 and other mixed oxides. Si mainly exists in the oxide layer in the form of SiO2. SiO2 formed underneath the inner Cr2O3 layer and eliminated the voids around the Cr-depletion zone. The grain size of outer oxides decreases and the inner oxide layer becomes more denser and thinner with the increase in Si concentrations. The suitable addition of Si was confirmed as 3 wt%, in which the coating was endowed with excellent comprehensive microstructure and outstanding oxidation resistance at 600–700 °C.