Joining materials for high temp service

[micro72w]

Hello
I have a high temperature service item a .375OD, .035 wall tube. The service will be 500 - 750 deg C at 1000 psi internal pressure. The service will also be of a corrosive nature. I am considering 316 SST, Inconel 625 or Hasteloy X for the tube materials. I am considering welding or brazing the tubes together possibly with nickel. I am having trouble locating any high strength data on brazing materials such as the nickel. Oh, by the way I will have Hydrogen flowing through the tube, don't know if this is a problem with embrittlement?
Can anyone suggest a source for the material data or possibly another fastening material?

Thank you for any assistance

 

[metengr]

With your stated service conditions and internal pressure at 1000 psi, this is a pressurized component and, as such, should be designed using recognized standards, like ASME B&PV Code, Section VIII, Div 1. There are thickness formulas and allowable stress values that will guide you in selecting material.

Using the highest temperature of 750 deg C as your design basis, there will be limited tube materials. For proper selection taking into account reduced mechanical properties, creep deformation and creep rupture strength, I would recommend you review ASME Section II, Part D.

Last item, brazing is not recommended for these service conditions. I would weld.

 

[metman]

I would not be too quick to discount furnace brazing with Nickel baze alloy in Hydrogen atmosphere or in vacuum furnace.

AMS 4779 (BNi-4) is recommended as good heat resistant alloy for brazing of highly stressed parts.

I do not know the brazed strength of this particular alloy but should be in the range of 14ksi-32ksi single shear.

 

[metengr]

metman;
At 1000 psi internal pressure at 1300 deg F, you should be looking at butt welded, full penetration, strength welded joints. I would agree with you if this was an external attachment to a tube or for hot gas flowing internally at less than 15 psig pressure.