AMS 4764 brazing question

By p.petrikas Date 09-10-2009 15:24

I have one question about microstructure of braze coupons for AMS4764.

We found difference phenomenon on the brazability test for current lot .

Please see the attached file.

What is dark layer ( Layer B in attached file ) of fillet area under the base metal ?

Diffusion layer or Alloying ?

It is found small quantity at brazed joint between sheets,

but, it reached 0.0035" at the exposed fillet area for this lot.

If it is alloying, that is limited to 0.0015" depth in our customer requirements.

Attachment: AMS4764_photo.pdf (350k)

By Tomwalz (*)

Date 09-18-2009 18:14

We braze carbide, cermets, ceramics, etc. to steel with AWS Bag alloys. We create a physical bond as well as a chemical (intermetallic) bond.

If I were analyzing these pictures as though they were our joints I would say that the first one showed little if any intermetallic formation while the second one showed a very nice intermetallic layer and was a much stronger bond.

Tom