By -
Date 04-04-2005 12:16
I agree with Mr. Avery. Over approximately 800F, you start entering the range of what is called "embrittlement stage." A 309L, which has a ferrite number of approximately 12-18FN is quite suseptible to this condition. An inconel is a pure austenitic material and has no ferrite so this condition is not in the equation.
CM
Mr. Avery's advise is very good. (I've had him personally help me solve a problem once, and he hit it right on the nose) For constant temperature service, the austinitic filler is perfectly fine at the listed temperatures. I don't think Mr. Avery was talking about cyclic service though. If you have temperature cycling, the inconel is preferred for the reasons MB Simms states. (Thermal stress/fatigue)