Effect of Post-Treatment Methods on the Performance of 600 ℃-Resistant Phosphate Coatings

Phosphate coatings are widely applied to protect compressor blades in aero-engines.After spray deposition，these coatings are typically subjected to high-temperature thermal curing or vibratory finishing.However，limited research has been conducted to date on how these treatment methods affect the coating’s microstructure and corrosion resistance.In this study，an organophosphate coating was selected as the research object and subjected to three post-treatment processes:curing at 560 ℃(the original factory process，denoted as Process A)，curing at 350 ℃(the process adopted in this work，denoted as Process B)，and curing at 350 ℃ followed by vibratory finishing (adopted in this work，denoted as Process C).The performance of the three coatings was tested and evaluated using scanning electron microscopy (SEM)，a six-anda-half-digit multimeter，and an acidic salt spray chamber，among other methods.The results showed that the coatings exhibited distinctly different surface colors after the three post-treatments.Marked differences in surface morphology were also observed:the Process A coating surface was characterized by dense lamellar coverage，and the coating internal compactness reached approximately 87%；the Process B coating surface appeared as a loose granular structure with more internal pores，with a coating internal compactness of approximately 80%.Compared with the Process B coating，the surface morphology of the Process C coating changed dramatically，whereas its internal structure was almost unchanged.Results from the acidic salt spray test，resistivity measurements，and electrochemical polarization curve tests consistently indicated that the corrosion resistance of the coating subjected only to 560 ℃ curing (Process A) was moderate，while the coating cured at 350 ℃(Process B) exhibited the best corrosion resistance.In contrast，the coating cured at 350 ℃ followed by vibratory finishing (Process C) showed the poorest corrosion resistance，demonstrating that vibratory finishing severely deteriorated the corrosion resistance of the coating.This work provided reference data for selecting post-treatment schemes for coatings in engine manufacturing and was of great significance and practical value for balancing the comprehensive performance of such coatings.