Microstructure and corrosion behaviour of plain carbon steel–B₄C composite produced by GTAW method in 3·5 wt-%NaCl solution

Abstract

In this work, the corrosion behaviour of metal matrix composite plain carbon steel–B₄C was studied in 3·5 wt-%NaCl solution. The composite was locally produced as weld band on plain carbon steel by means of gas tungsten arc welding process and using nickel as wetting agent. Samples from weld band, heat affected zone and base regions were extracted precisely, and electrochemical techniques including open circuit potential, linear polarisation resistance, electrochemical impedance spectroscopy, potentiodynamic polarisation in combination with SEM-EDX surface analysis and microhardness were used for characterisation. The results showed that hardness value of made composite increased significantly to 642 HV10. However, the corrosion resistance of composite region during 7 days (168 h) of exposure to 3·5 wt-%NaCl solution was slightly reduced. This was attributed to the fact that B₄C particles play as cathode site for oxygen reduction; therefore, they increase the corrosion rate slightly.

Keywords:

• Metal matrix composites
• Corrosion
• Electrochemical impedance spectroscopy
• Potentiodynamic polarisation
• SEM

Acknowledgements

Authors would like to acknowledge the Khorasan Razavi, Science and Research Branch, Islamic Azad University, Neyshabur, Iran for providing experimental facilities.