Materials and welding metallurgy

Protective coatings

A surface layer is not designed solely according to hardness. It must address the actual damage mechanism: wear resistance, friction reduction, corrosion resistance, a diffusion barrier, a thermal barrier or a combination of these requirements.

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Topic overview

A surface layer is not designed solely according to hardness. It must address the actual damage mechanism: wear resistance, friction reduction, corrosion resistance, a diffusion barrier, a thermal barrier or a combination of these requirements.

Non-diffusion: paints, enamels and linings. Diffusion: carburising, nitriding, carbonitriding and aluminising. Fusion-applied: overlay welding and cladding. Thermophysical: PVD. Thermochemical: CVD.

For welded structures, also assess the layer’s behaviour under heat: porosity, weld-metal contamination, HAZ alteration, distortion and formation of brittle interphases.

What the module covers

  • Protective layers and surface treatments
  • Layer function
  • Classification by character
  • Classification by technology
Educational content does not replace current standards, approved WPS/WPQR documentation or decisions by competent welding coordination personnel.