Testing the Hardness of Carbide

I had a question today about whether an end-user can test the hardness of carbide.

 

The official way to test carbide hardness is with a Rockwell tester or similar but nobody even pretends that this way is particularly accurate.

In a Rockwell test, pressure is applied slowly through a particularly shaped diamond point.  This has almost nothing to do with how carbide is used in the real world.  Because of this, it is not uncommon to see carbide grades with a lower Rockwell value out wearing carbide grades with a higher Rockwell value.

Tungsten carbide is tungsten carbide grains in a cobalt matrix. When you test tungsten carbide hardness you are mostly testing the amount of cobalt in it.  You are also testing grain size to a certain extent as well as testing how well the carbide is made.

Official ratings for carbide hardness are ballpark estimates at the best and don’t necessarily have much to do with how well the carbide will perform.

Typically in our industry, when someone says they are interested in carbide hardness what they are really interested in is carbide performance.  Carbide used to be considered either hard for long wear or tough to prevent breaking.  We have carbide tips in many different grades that will perform the best for a particular application.  Our Cermet II grade tips are extra long wearing.  Our Super C grade tips is both harder and tougher than most carbide grades, making it ideal for many applications.  We also have a Nail cutting grade that is very tough and less prone to breakage, even in the toughest applications.

 

 

However we now see carbide with a lower transverse rupture strength that is actually tougher and carbide with a higher transverse rupture strength.

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