Is carbide heat treatable?

[ahidley]

The reason that I ask this is because in the past I have silver soldered carbide to a boreing bar and the carbide just didn't seem to last as good as before it was heated during the silver soldering process.
Is it required to re harden and temper after silver soldering which would be an annealing process?

[Bob La Londe]

The reason that I ask this is because in the past I have silver soldered carbide to a boreing bar and the carbide just didn't seem to last as good as before it was heated during the silver soldering process.
Is it required to re harden and temper after silver soldering which would be an annealing process?

I would sure like to know that since I've seen carbide that looks like it was brazed on as well.

[bborr01]

I've silver soldered a ton of carbide and never noticed the difference. But no, I don't think there is any need to try to harden it.

Brian

[MattiJ]

Can't harden and shouldn't soften. Might crack or something tho.

If I remember correctly some grades of tungsten carbide are more suited for brazing than others. Wettability was one potential problem, cracking also if you apply too much heat.

[Willy]

Can't harden and shouldn't soften. Might crack or something tho.

If I remember correctly some grades of tungsten carbide are more suited for brazing than others. Wettability was one potential problem, cracking also if you apply too much heat.

Cracking can also occur if the brazed joint is allowed to cool too fast. Another issue at times is not enough braze materiel between the steel and the carbide. Due to the large expansion ratio of carbide it can crack or break down because the cushion it sits in is not large enough to accommodate it's growth when in use.

I believe that carbide with high levels of cobalt binders, although demonstrating good wetability, tend to be softer. Been a few years since I've done a lot of this. I do remember however that the brazing alloy I used had a high silver content and a melting temp between 1100-1300°F. I have even used silver baring solders with melting temps in the 6-700°F range with success.

Hardness as mentioned however should not change during the process, at least not to my knowledge.

[Magicniner]

The reason that I ask this is because in the past I have silver soldered carbide to a boreing bar and the carbide just didn't seem to last as good as before it was heated during the silver soldering process.
Is it required to re harden and temper after silver soldering which would be an annealing process?

It is almost certainly the case that your Tungsten Carbide tip isn't a lump of Tungsten Carbide, it's a cemented composite with particles of Tungsten Carbide in a less brittle metallic binder.
No, you can't soften or harden it.

- Nick

[MattiJ]

It is almost certainly the case that your Tungsten Carbide tip isn't a lump of Tungsten Carbide, it's a cemented composite with particles of Tungsten Carbide in a less brittle metallic binder.
No, you can't soften or harden it.

- Nick

And its not even just Tungsten carbide. Common in English to talk about Tungsten carbide but almost all of the steel cutting grades are mixes of different carbides(tungsten- tantalum- boron- titanium- carbide) and binder.

[ahidley]

Humm.... I think Nick answered the problem.
So....if my lumps of so called carbide aren't really carbide then what kinds of so called carbide are utilized on brazed boring bars? Or what kinds can be silver soldered or if the list is shorter, what kinds cannot be silver soldered?

[J Tiers]

Carbides are just compounds of carbon and other elements with a particular crystal structure, just as diamond is carbon with a particular structure.

Because it is brittle, as hard things tend to be, it is powdered and put in a binder material that holds the particles, with the toughness to avoid breakage. Used to be cobalt was used, might be other things now. The brazing/soldering in is done to the binder.

The carbide powder is a mix of various types of carbide, to get particular qualities. It's not "so called carbide", as if it were a cheap substitute, that's what "carbide" is in "machine shop speak"..

[Magicniner]

The reason that I ask this is because in the past I have silver soldered carbide to a boreing bar and the carbide just didn't seem to last as good as before it was heated during the silver soldering process.
Is it required to re harden and temper after silver soldering which would be an annealing process?

I'll bite ;-)
What is the brand or source of the Tungsten Carbide which you are silver soldering to your boring bar?

[Duffy]

Did you consider that in some silver brazing applications there is a cushion of copper foil interposed between the carbide and the steel holder? At least that is my understanding of brazing carbide tips to steel holders.

[MattiJ]

I'll bite ;-)
What is the brand or source of the Tungsten Carbide which you are silver soldering to your boring bar?

You might be into something..
Maybe OP has pieces of HSS ?
Or uncoated carbide lathe inserts if he knows how it was cutting before brazing?