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Brazed Tooling Suitable for Coating

11/09/2015 6:09 PM

The company I work for has been making steel tools with cemented carbide tips brazed to the steel for many years. Now customers want the tools coated. The coating companies are telling us that the braze alloy can not contain zinc, but cannot recommend a brazing alloy that does not contain zinc. We torch braze and the alloys that I find either are not strong enough or need to be used in a vacuum. The alloy we use is BAg-22. Any suggestions

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#1

Re: Brazed Tooling Suitable for Coating

11/09/2015 6:56 PM

Perhaps one of the Pallabraze alloys.

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#2

Re: Brazed Tooling Suitable for Coating

11/09/2015 7:27 PM

How does boron-silver impinge on the no-zinc criterion, or are you using code letters in your definition?

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#3

Re: Brazed Tooling Suitable for Coating

11/09/2015 8:16 PM

coated with what?

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#5
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Re: Brazed Tooling Suitable for Coating

11/10/2015 4:02 AM

Possibly TiN or similar for wear resistance, I can't see why there would be a zinc restriction for a wax coating but we need Harvey to clarify.

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#4

Re: Brazed Tooling Suitable for Coating

11/09/2015 9:00 PM

What is the coating for? I would try to find a coating that worked...or possibly dip the carbide tips in wax or plastic, I'm thinking the tips don't need to be coated...?

http://www.carbideprocessors.com/pages/brazing-carbide/brazing-alloy-choosing-the-right-braze-alloy-for-specific-applications.html

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#7
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Re: Brazed Tooling Suitable for Coating

11/10/2015 10:03 AM

Thank you all for the information. The coating is for wear. It is TiN or AlTin and is put on in a vacuum chamber at 900 degrees F. The coating is 3 to 4 microns thick and greatly improves tool life. The limited information from the coating companies is that the zinc out gasses and contaminates the chamber. Some of the alloys for brazing require too high of heat and some are not strong enough to hold the tips in place during machining.

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#9
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Re: Brazed Tooling Suitable for Coating

11/10/2015 10:43 AM

Zinc (& lead) are nasty in high vacuum at temperature. These metals evaporate & coat everything in the chamber as well as the chamber surfaces. They will also evaporate out of alloys such as brass so I can see why the coating company say not to use zinc.

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#10
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Re: Brazed Tooling Suitable for Coating

11/10/2015 3:18 PM

Maybe coat the tool first? just spitballing...

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#12
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Re: Brazed Tooling Suitable for Coating

11/11/2015 1:02 AM

The best recommendation I have seen thus far is BAg-22 49% silver with manganese...doesn't seem to flow well, but with proper methodology will work...best alternative to cadmium and/or zinc....

http://www.carbideprocessors.com/pages/brazing-carbide/brazing-tungsten-carbide.html

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#6

Re: Brazed Tooling Suitable for Coating

11/10/2015 7:29 AM

Carbide Processors may a zinc free brazing alloy. They are on the west coast and thats what they specialize in.

They are available. http://www.lucasmilhaupt.com/en-US/products/fillermetals/carbidebrazingalloys/2/

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#8
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Re: Brazed Tooling Suitable for Coating

11/10/2015 10:16 AM

Yes, vacuum grade, their blog speaks to this, so I expect they have i.

being a specialty = $$

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#11

Re: Brazed Tooling Suitable for Coating

11/10/2015 11:14 PM

Handy and Harmon makes an alloy of 72% silver and 28% copper (Handy and Harmon 721) which would probably work well for your application. It is an eutectic with a melting point of 1435oF, contains no zinc, is available in a 400 mesh powder and rods, and is a proven alloy for brazing. It has been around for at least 45 years or more. Although the components, silver and copper, would seem to make it a soft alloy it is not. It is very strong as a brazing alloy. It does not have to be used in a vacuum, simply a hot oxy-acetylene torch is sufficient.

http://www.handyharmancanada.com/TheBrazingBook/Section%203/Part%201.htm

Contact Handy & Harmon and obtain a sample. You will never know if it works or is the best one unless you try it.

At one time this alloy was used as part of an unique formula for dental amalgam, the silver colored dental filling material.

http://www.pipeweldrig.com/files/weld/Brazing%20book%20.pdf

Good Luck, Old Salt

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#13
In reply to #11

Re: Brazed Tooling Suitable for Coating

11/11/2015 9:16 AM

GA and another vote for 721.

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#14
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Re: Brazed Tooling Suitable for Coating

11/11/2015 9:45 AM

Thank you Old Salt, I completely missed them in my search, sounds like what I need I will call for a sample

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#15
In reply to #14

Re: Brazed Tooling Suitable for Coating

11/11/2015 12:30 PM

Better yet, when you call them for a sample of the 721, ask them what they would recommend for your application. They should know there complete product line and what the properties are. Most of my knowledge is with the 721 and utility maintenance use type alloys.

Give it a try. All it takes is a phone call.

Good Luck, Old Salt

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