Weld Failures in Powder Forgings
Several powder forged parts were provided for evaluation.
A failure developed in these parts welded to a carbon steel steering arm where a weld bead pulled away after assembly. A dark stain was observed beneath the weld bead in each case.
Additionally, the surface of the powder forged parts developed blisters during the forced drying portion of the paint cycle.
The examination of a solvent extract of the parts using GC/MS found the pores in the microstructure contained significant amounts of different decanoic acids. It is believed that, during the welding operation, these compounds were carbonized and produced a layer that interfered with formation of a proper weld bond.
Further, the blistering that developed during painting likely resulted when these compounds vaporized. The source of the organic compounds cannot be exactly determined from this investigation, but based on knowledge of the manufacturing process, it is suspected that they are present from die lubricant used in the production of the parts.
Failure Analysis Examples
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