Nb–Cr complex carbide coatings on AISI D2 steel produced by the TRD process

  • Fabio Enrique Castillejo
  • Jhon Jairo Olaya
  • José Manuel Arroyo-Osorio
Technical Paper

Abstract

Nb–Cr complex carbide coatings were produced onto AISI D2 steel by the thermo-reactive diffusion process to improve the surface hardness and corrosion resistance of this tool steel. The carbide coating treatment was performed using molten borax added with ferroniobium, ferrochrome and aluminum at temperatures of 1,223, 1,293 and 1,363 K during 2, 3, 4 and 5 h. The coating layers were characterized by optical and Scanning Electron Microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and X-ray fluorescence spectrometry. The coating growth rates were evaluated, and a model of the layer thickness as a function of the treatment time and temperature was established. The hardness of the coating was measured by nanoindentation, and its resistance to corrosion was evaluated with electrochemical tests of potentiodynamic polarization. The produced carbide layers presented a homogeneous thickness as well as an improved hardness and corrosion resistance as compared to the uncoated steel.

Keywords

Thermo-reactive diffusion coatings Nb–Cr complex carbides Corrosion Hardness 

List of symbols

x

Carbide layer thickness, cm

D

Diffusion coefficient, cm2/s

t

Processing time, s

R

Gas constant, J/(mol K)

Q

Activation energy, kJ/mol

T

Absolute temperature, K

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Copyright information

© The Brazilian Society of Mechanical Sciences and Engineering 2014

Authors and Affiliations

  • Fabio Enrique Castillejo
    • 1
  • Jhon Jairo Olaya
    • 2
  • José Manuel Arroyo-Osorio
    • 2
  1. 1.Departamento de Ciencias BásicasUniversidad Santo TomásBogotá DCColombia
  2. 2.Departamento de Ingeniería MecánicaUniversidad Nacional de ColombiaBogotá DCColombia

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