Evaluation of mechanical, metallurgical, and hot corrosion-erosion behavior of plasma sprayed Ni22Cr10Al0.8Y/30 %Cr3C2 /10 %h-BN/10 %Mo composite coating

Abstract

In this work, plasma-sprayed coatings at high temperatures are examined for microstructure, corrosion, and erosion behavior. Utilized as a feedstock material for plasma spraying, the coatings were composed of a blend of Ni22Cr10Al0.8Y, Cr₃C₂ h-BN, and Mo in varying weight proportions. As the substrate material for coating, ASTM A213, T22 boiler steel was employed. In a liquid salt environment with Na₂SO₄–60%V₂O₅, thermocyclic hot corrosion studies were conducted for 50 cycles at 700 °C on both bare and coated steels. Thermogravimetric analysis was used to evaluate the hot corrosion kinetics, and the erosion properties of the Ni22Cr10Al0.8Y/Cr₃C₂/h-BN/Mo composite coating that was plasma-sprayed onto T22 boiler steel alloy were investigated. An air jet erosion tester was used for this assessment at three different temperatures (200 °C, 400 °C, and 600 °C) with impingement angles of 30° and 90° and a velocity of 40 m/s. Microhardness and microstructure analyses were performed on the coated samples. For characterization, this investigation included energy-dispersive spectroscopy, scanning electron microscopy (SEM), X-ray mapping, and X-ray diffraction (XRD). The results of the study showed that, in comparison to the uncoated substrate, the Ni22Cr10Al0.8Y/Cr₃C₂/h-BN/Mo coated substrates exhibited 89 % higher resistance to hot corrosion and, at a 90° impact angle, the coating exhibited 55 % higher erosion resistance than the uncoated substrate. In contrast to the uncoated steels, the coated substrate had lower parabolic rate constant values and adhered to the parabolic rate law of oxidation. Because of the high stability of molybdenum and chromium carbides as well as the production of a protective oxide layer of nickel, chromium, B₂O₃, and MoO₂ oxide at high temperatures, there is an enhanced resistance to erosion and corrosion.