Since you only have a 150C margin between processing and operation, brazing is tough as most alloys in that range (Cu-Ag-In) will dilute the Au. I like metman's idea of creating a mechanical joint by shrink fitting. If you also want a metallurgical bond, gold plate the ID of the tube then...
The use of an alumina tube would certainly remove the delta CTE risk, but makes brazing more difficult due the metallization metman described. An atlernative to metallization is using an active metal braze (ABA). ABA's, if you're not familiar, contain highly reactive metals like Ti or Al which...
One other option which may be simpler is to use an Fe-Co-Cr Stainless Invar tube instead of SS - if available. It will greatly reduce the CTE mismatch, but I think there is a phase change Invar goes through which dramtically raises CTE which may be below 600C. Also it may need to be Ni plated...
The silver-copper and silver-copper-indium alloys are good choices below 800C. I think the silver-copper eutectic alloy BAg-8 is a good choice, but not sure how well it will wet bare SS, and you won't get near the strength of the other alloys mentioned before.
There is a major risk in your...
There are several precious metal braze alloys which offer good mechanical and chemical resistance at 600C, will readily wet clean bare SS (brazed in vacuum or hydrogen) and give you a good chance of filling the tight joint you have in your design. Some options are BAu-4 (82Au 18Ni - sol/liq...
This should have been my first post: A water quench will result in a higher hardness than oil. You must also consider your temper temperature when considering toughness. You may get a greater toughness at a given temper temp after water quench due to slightly higher strength. So in that...
Granted water has a greater cooling capability than oil, I think the 0.25 thickness will erase that difference. Dig up some end quench data and you'll see a fairly flat hardness for at least the first quarter inch for most alloys (like 4130) designed to have high hardenability. And that...
....and to answer your customer's concern, in our case we demonstrated adequate material response to the quench and temper process, which resulted in typical (or at least minimum) strength and toughness (although not tested) properties. Also, you can sell them away from a water quench with the...
Tony - What are you customer's final strength requirements? I recently performed through hardenability testing on a 4"L x 4" dia bar of 4340 (different material I realize) which was 10bar nitrogen gas quenched. The quench rate was slower than a comparable water quench rate. It was...
