Thickness-Induced Phase Evolution and Mechanical and Tribological Performance of Arc-Sprayed FeCrAl Coatings

In this study, we examined the influence of coating thickness on surface roughness, hardness, phase composition, and tribological behavior of arc-sprayed FeCrAl coatings deposited on steel substrates. We measured coating thickness, phase composition, and surface roughness using optical microscopy, X-ray diffraction (XRD), and profilometry, respectively. Results showed that surface roughness decreased with increasing coating thickness due to improved splat coalescence. However, Rockwell hardness remained nearly constant (at approximately 95 HRB), denoting a limited dependency on coating thickness. Using pin-on-disk tribometry, we found that the thickest coating showed the highest coefficient of friction (CoF, mean value of 0.864). This is because there is an in-creased tendency for the formation of hard oxide phases (Cr₂O₃ and Al₂O₃) in thicker coatings. These oxides increased friction by generating abrasive debris during sliding. The novelty of this work is that CoF is sensitive not only to surface morphology but also to thickness-dependent phase composition, whereas most previous studies found that CoF was primarily correlated with surface roughness only. Our research findings show that both microstructural and phase composition behavior during deposition are crucial for optimizing the friction and wear properties of FeCrAl coatings in high-temperature, steam-rich applications. Therefore, accurate control of oxidation behavior as a function of coating thickness can lead to more durable, reliable coatings in those environments.