Kinetics of electrochemical boriding of low carbon steel

Kartal G., Eryilmaz O. L., Krumdick G., Erdemir A., Timur S. İ.

APPLIED SURFACE SCIENCE, vol.257, no.15, pp.6928-6934, 2011 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 257 Issue: 15
  • Publication Date: 2011
  • Doi Number: 10.1016/j.apsusc.2011.03.034
  • Journal Name: APPLIED SURFACE SCIENCE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.6928-6934
  • Keywords: Electrochemical boriding, Growth kinetics, Activation energy, Boride layer thickness, ALLOYING ELEMENTS, GROWTH-KINETICS, IRON, MECHANISM, LAYERS, PHASE
  • Istanbul Technical University Affiliated: Yes

Abstract

In this study, the growth kinetics of the boride layers forming on low carbon steel substrates was investigated during electrochemical boriding which was performed at a constant current density of 200 mA/cm(2) in a borax based electrolyte at temperatures ranging from 1123K to 1273K for periods of 5-120 min. After boriding, the presence of both FeB and Fe2B phases were confirmed by the X-ray diffraction method. Cross-sectional microscopy revealed a very dense and thick morphology for both boride phases. Micro hardness testing of the borided steel samples showed a significant increase in the hardness of the borided surfaces (i.e., up to (1700 +/- 200) HV), while the hardness of un-borided steel samples was approximately (200 +/- 20) HV. Systematic studies over a wide range of boriding time and temperature confirmed that the rate of the boride layer formation is strongly dependent on boriding duration and has a parabolic character. The activation energy of boride layer growth for electrochemical boriding was determined as (172.75 +/- 8.6) kJ/mol. (C) 2011 Elsevier B. V. All rights reserved.