Optimization of Cored Wire Arc Spraying of Amorphous FeCrNiSiWNbB Coating; Hot-Corrosion and High-Temperature Erosion Evaluations

Abstract

Protective coatings are the most common solution to prevent high-temperature erosion, oxidation and especially hot corrosion of boiler tubes. One of the best protective coatings for boiler tubes is amorphous/nanocrystalline coatings, which can be deposited by different thermal spray methods especially via arc spraying as a low-cost and portable method. The aim of this study is the fabrication and characterization of Fe-based amorphous/nanocrystalline coating designed for boiler tube via the low-cost FeCrNiSiWNbB cored wire using the ferroalloy powders. This work was focused on the reducing of the porosity of coatings by optimization of the arc spraying parameters using Taguchi design of experiment, which was verified by microhardness measurements and metallography experiments. The microstructure, composition and phase constitution of the optimized coating were characterized by scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, and selected area electron diffraction techniques. The erosion resistance and hot corrosion behavior of the modified coating were investigated by high-temperature erosion and hot corrosion (type II) tests, respectively. It was found that optimal FeCrNiSiWNbB coating represents a significantly higher hot corrosion resistance rate, 92, and 86% increase in comparison to carbon steel substrate and pure Fe coating, at 600 °C. Additionally, the high-temperature erosion resistance rate of optimized FeCrNiSiWNbB coating enhanced 26, and 14% at 600 °C in comparison to the pure Fe coating and plain carbon steel substrate respectively.