Parametric optimization, corrosion erosive wear and XPS response of FeCrCoAlTiB coating on Q235 steel substrate by HVOF spraying using Taguchi method

Fe₃₂Cr₂₁Co₂₁Al₁₆Ti₅B₅ (Coating 1) and Fe₄₃Cr₁₆Co₁₂Al₁₄Ti₅B₁₀ (Coating 2) were deposited on Q235 steel substrates using high-velocity oxy-fuel (HVOF) thermal spraying. Slurry erosion resistance was evaluated using a jet-type erosion tester, and surface degradation mechanisms were analysed through microstructural characterization. Material removal occurred through a combination of ploughing, cutting, platelet formation, abrasive grooving, and cracking. Parametric analysis revealed that impact velocity was the dominant factor influencing erosion, contributing approximately 65–68% to the total wear rate, followed by impingement angle (≈ 30–32%). The relative significance of control parameters followed the order: impact velocity > impingement angle > erodent feed rate > erodent size. Scanning electron microscopy indicated that erosion mechanisms varied with impingement angle, with micro-cutting, mixed cutting, and furrowing dominating at low angles, while platelet formation governed material removal at near-normal impact. Both coatings exhibited the formation of protective passive layers, as evidenced by higher corrosion potentials (E_corr) compared with the substrate. Taguchi analysis identified the optimal erosion-resistant conditions as an impact velocity of 10 m s⁻¹, impingement angle of 30°, erodent feed rate of 160 g min⁻¹, and erodent particle size of 105 μm. Overall, the results demonstrate that erosion behaviour is governed by impact-driven deformation mechanisms, with platelet detachment acting as the primary failure mode at higher impingement angles.