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Chrome / Chromium Carbide Coating (CrC-DHC)

Case Study Characterization of CrC Coating:

Material:

  • Low carbon steel

Samples:

  • Steel strip (1''x1''x0.03'')

The Characterization Included the Following Methods:

  • SEM analysis of surface morphology
  • Metallographic examination
  • Microhardness testing
  • X-ray diffraction
  • High resolution SEM

Results:

  • The surface morphology of sample 1 is shown in Figure 1 and is characterized by spherical particles 7-8 µm in diameter
  • The microstructure in the cross-section of sample 1 in Figure 2 reveals a uniform coating thickness of 12 µm from both sides
Figure 1: CrC Coating Surface Morphology of Sample 1 Figure 2: Uniform Coating Thickness in Sample 1
  • No defects, such as porosity or contamination, are revealed within the coating or at the interface
  • The base material has a ferrite microstructure
  • Higher magnification photos of the microstructure appear in Figures 3 and 4
  • The micro-hardness indentations are seen in Figure 3. The micro-hardness level was found to be 3000-3500HV within the coating
Figure 3: Micro-hardness Indentations Figure 4: SEM Photo Shows No Defects Within the Coating or at the Interface
  • High Resolution (HR) SEM was applied to examine the grain structure of the coating from the surface. Figures 5 and 6 confirm the nanostructure of the coating to be 20-30nm
Figure 5: High Resolution SEM Photo of the Surface, x100.000 Figure 6: Appearance of Nano-Crystals on Surface

Other Characteristics:

  • Phase content of the coating: Cr7C3 + Cr23C6
  • Micro-hardness of the layer: 2,000 - 2,200 HV
  • Micro-hardness of the base metal: 700 - 800 HV
  • Layer thickness: 0.0004'' - 0.0006''
  • Very low coefficient of friction
  • No coarsening of the base metal