A welding process developed by Federal-Mogul Powertrain is being used to overcome the sealing challenges that can occur when joining dissimilar metals in the manufacture of automotive turbocharger gaskets.

The gasket for a turbocharger outlet flange comprises a thick steel distance layer that is aluminum-coated for corrosion resistance and, to reflect heat, sealed on both sides by functional stainless steel layers, each with a sealing bead. To avoid handling multiple parts, all three layers are welded together.

When stainless steel and aluminum-coated steel are welded together, a reaction can occur that compromises the gasket seal. Image credit: Federal-Mogul PowertrainHowever, this can create issues with sealing uniformity because the aluminum coating can react during welding. This can create bubbles that generate high spots on the sealing face, leading to variations in contact pressure.

An approach developed and now in use by Federal-Mogul Powertrain has three holes blanked out of the distance layer and three dimples created in both of the sealing layers. This ensures accurate location of the separate components, allowing the functional outer layers to be spot-welded to each other through the dimples without affecting the material in the distance layer. This, in turn, unites the whole assembly.

The process has been in high-volume production at the company's sealing production site in Herdorf, Germany, for several months and is said to have proven successful. The company says it believes the process will be equally effective for other applications where functional gasket layers are combined with a coated distance layer or heat shield, on both gasoline and diesel engines.