Effect of Annealing Time on Coating Microstructure, Frictional and Electrochemical Behavior of Galvannealed Interstitial-Free Steel

• Published in: Journal of materials engineering and performance 2023-07, Vol.32 (13), p.5932-5945
• Main Authors: Kancharla, Harikrishna, Mandal, G. K., Kumar, Rakesh Ranjan, Chakraborty, Anindita, Singh, S. S., Mondal, K.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Engineering Design; Materials Science; Quality Control; Reliability; Safety and Risk; Technical Article; Tribology
• ISSN: 1059-9495; 1544-1024
• DOI: 10.1007/s11665-022-07527-4

The present study deals with the effect of isothermal holding time (10, 20, and 30 s) at a fixed annealing temperature of 500 °C on the formation of various Fe-Zn intermetallic phases during galvannealing treatment of a galvanized (GI) interstitial-free steel, and its correlation with the friction behavior determined by scratch test and electrochemical behavior in a freely aerated 3.5 wt. % NaCl solution. Pure Zn coating in GI specimen transforms to the various Fe-Zn intermetallic phases consisting of overlay zeta (ζ) phase with elongated rod type morphology, compact delta (δ) phase as well as a very thin layer of gamma (Γ) phase at the coating–substrate interface during isothermal annealing treatment of the GI sheet. The ζ phase has been noticed to get consumed by the more compact δ phase and increase in thickness of the thin Γ phase layer at the coating–substrate interface as iron content in the coating increases with an increase in galvannealing holding time. The galvannealed (GA) coating prepared at a galvanneal time of 30 s has the lowest coefficient of friction (COF ~ 0.26) as compared to 20 s (COF ~ 0.31) and 10 s (COF ~ 0.36), and the lowest corrosion rate (CR ~ 0.184 mm/y) as compared to 20 s (CR ~ 0.214 mm/y) and 10 s (CR ~ 0.227 mm/y). The dominance of compact and crater-free coating surface morphology along with the lowest zeta to delta (ζ/δ) phase fraction results in the lowest COF as well as the lowest corrosion rate of the GA coating prepared at a galvanneal time of 30 s.