Welding Tips and Tricks

Hi folks,

Whilst inspecting my turbo I found a crack in my exhaust housing.

It's definitely worth repairing - as long i can successfully weld it and re machine it.

What's people's thoughts on Tig welding this, inc techniques and filler rod?

Any advice appreciated.

Type of cast stainless would be interesting to know...

A quick google seems to indicated that CF8C and CF8C-plus cast stainless is often used in this kind of high-temp application:

http://www.asminternational.org/emails/ ... 610p27.pdf

CF8C
-----
Cr 19
Ni 10
Mn <1
Nb 0.8
Mo 0.3
C 0.07
N 0.02
Si 1.0

CF8C-Plus
------------
Cr 19
Ni 12.5
Mn 4
Nb 0.8
Mo 0.3
C 0.1
N 0.25
Si 0.5

So that could be a pointer..

A little further digging for filler rod throws some hints at using inconel 117 filler rod when welding this kind of material to keep the high temp resistance intact:

http://www.specialmetals.com/assets/smc ... /we117.pdf

Although I suspect you'll be fine with any stainless filler rod that's close to the same composition of alloying elements as the base metal.

As to fixing it.. You'll probably have to play 'chase the crack' and grind out and 'V' the crack until it's all gone and you only have intact base metal left. May tunr out that the crack goes a looong way though and the housing is not really salvageable..

If it is OK, then start building up the material again with good gas coverage in short sessions to stop the base metal overheating and once it's all built back up and overbuilt a little have the housing re-machined as it will likely draw and possibly warp the housing a bit during the process and inevitable shrinkage of the welds.

Bye, Arno.

Have you contacted Tial about the warranty? They would also know the type of stainless used.

If it was me I would use it as a paper weight. The stress and heat cycling the turbine housing goes through would make any repair the weak point. Worst case you toast the turbo and the engine.

Yes, I have been in touch with TiAl but not heard anything back yet!

Like you say, probably best to buy a new one and use the old one as a paper weight!

It's probably repairable, but whether it will be successful Is a gamble. And at the end of the day - is it worth all the time and effort to find out.

Cheers.

Not tackled this yet, but a machinist friend of mine said inconel is difficult too machine!?

Can anyone recommend a stainless filler rod to use?

I haven’t plucked up the courage to tackle this job yet. Gonna have a go soon but I need a smaller carbide burr to clean the crack out.