brazing Inconel 718 to SS 316L

By eli Date 02-26-2008 06:59

dear all,
we perfomed several test to understand the brazing results between #7 Inconel 718 tubes in a SS316L manifolds using AMS4787 brazing alloy.the hole dimesions in the manifolds are 3.26mm while the inconel tubes 3.19mm, and the brazing Max T is 1000°C. our goal is to see the brazing material come out from the holes, but even nickel palting the Inconel tubes there ar ealways some tubes that seem to ahve no brazing material around. someon can tell me which are the value of the parameters that we need to take into account? ( time, T, optimum gap beetween tube and hole etc??)
thanks in advance
eli

By JLiguori Date 04-03-2008 13:02

Eli,
I assume you are vacuum brazing these materials? The joint gap, cleaning, and atmosphere are very important with these materials. Nickel plating is generally considered to be necessary if you are not brazing in the low 10-5 Torr or better range. Try staking the tubes or pre-placing foil in the joint to keep the tube centered and the gap uniform. The temperature is fine, time can vary quite a bit and still yield good results. We braze these materials often with good results. Feel free to contact me directly.

Justin Liguori
Scarrott Metallurgical
www.scarrott.com