Materials and welding metallurgy

Dissimilar-material joints

A dissimilar joint is a material system in its own right. Weld metal is mixed from three sources, the two interfaces develop different microstructures, and differential expansion, diffusion and corrosion can dominate over static strength during service.

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Topic overview

A dissimilar joint is a material system in its own right. Weld metal is mixed from three sources, the two interfaces develop different microstructures, and differential expansion, diffusion and corrosion can dominate over static strength during service.

Has stability of the mixed zone and both interfaces been demonstrated for the full thermal, corrosive and mechanical life?

Weld chemistry is controlled by filler and dilution from both parent materials.

Each side may need different preheat, maximum interpass and thermal history.

What the module covers

  • Dissimilar-material joints — dilution, interfaces and life
  • 1. Mechanisms that must be assessed
  • 2. Typical material combinations
  • 3. Qualification sequence
  • Design and fabrication checklist
  • Practical rule
Educational content does not replace current standards, approved WPS/WPQR documentation or decisions by competent welding coordination personnel.