Electron beam welding of Ni/Co/Fe alloys, pre-treatment

[Feldmann359]

Dear Colleagues,

Do you know if it is beneficial for the welding result to remove scales from superalloys prior to EB welding?

We have many years experience with alloy 75 EB welding. After mechanical machining, in some cases there is a time duration of several weeks (storage under ambient conditions, dry air) until welding.

No acid pickling etc will be done before welding, with excellent results regarding weld seam structure and stability.

So at the moment, I am planning welding tests of various other super alloy. Does somebody know wheter it may be important to perform pickling prior to EB welding, especially for alumina scale forming alloys like Kanthal?

Best regards
Feldmann

 

[Goahead]

Cleanliness before welding is a standard requirement. Alumina scale if present should be removed.
Depending on joint configuration and thickness, planned testing will probably confirm that no pickling is required, except in severe cases.

http://www.welding-advisers.com/

 

[Feldmann359]

Thanks for your comment, our standard procedure before welding is ultrasonic cleaning in degreasing agent. Do you know if superalloys form scales (alumina oxide or chromium oxide) which are not visible for the naked eye and that are anyway detrimental with regard to welding performance? Or is is ok if the material is still as metallic bright as is comes from turning/milling?
Thanks very much in advance!

 

[TVP]

Your procedure of turning/milling --> ultrasonic cleaning with alkaline degreaser should produce acceptable welds. The formation of aluminum or chromium oxide requires some type of elevated temperature (hot rolling, forging, etc.), so as long as your parts have the surface layer machined off, there should be no problem.