Titanium exhaust parts rarely fail in the middle of a straight run. The first places to go are the joints, the welds where a tube meets a flange, a collector, a muffler body or a hanger. Those are the points where the metal is already hot, restrained and cyclically loaded.
Failing at a weld is not automatically the welder's fault. Even a perfect weld concentrates stress, and a design that gives the joint nowhere to move will eventually crack regardless of how well the bead was laid down.
Titanium must be welded in an atmosphere that excludes air, inside and out. On a new part that is straightforward, because the fabricator controls the whole assembly. On a used part it is much harder, because the pipe is contaminated with soot and deposits, access is limited by the car, and the surrounding material is already work-hardened.
Contamination is the main enemy. Oil, soot or oxidation picked up during the repair will be drawn into the weld and produce a brittle joint that cracks again quickly. A repair that has not been cleaned properly is worse than no repair at all.
A crack has to be followed to its end before it can be closed. Grinding back to sound metal, then welding from the end of the crack toward the tip, stops the weld from finishing short and leaving a hidden initiation point. Stopping a weld in the middle of a crack almost guarantees a repeat.
Where a crack runs alongside an existing weld, the original bead is often removed and replaced rather than patched over. The same approach used for titanium fab components applies here, in that a repair should not create a new stress raiser.
Thin-wall titanium that has been badly overheated is usually not worth repairing. Once the surface has oxidised deeply the material has lost ductility, and any weld nearby will pull it apart. The same is true of a section that has been crushed or collapsed, or a muffler case cracked along a formed seam.
Corroded or pitted areas are another category. The wall that remains is thinner than the design intended, so patching simply moves the problem further along the pipe instead of solving it.
A splice is often a better answer than welding on the crack itself. Cutting out the damaged length and replacing it with new tube gives clean, uncontaminated metal to weld and removes the fatigued region entirely. The replacement should match the wall and diameter so that the joint does not become a step in the flow.
Fit-up is everything for this kind of work, and it is the same discipline behind consistent TIG titanium welding parts. Tack, check alignment, purge, then complete the joint with full shielding on both faces.
Base the decision on how much sound metal is left, how much of the car has to come apart to reach the joint, and whether the failure is a one-off or a pattern. A single cracked hanger is easy to justify repairing. The third crack in a year on the same system is telling you something about the design or the way it is restrained.
Where the whole system is tired, replacing the affected section with a properly supported part is often cheaper over a few years than repeated welding on material that is already near the end of its life.
