Tungsten Carbide Hardness Range

[ykang]

Dear Fellows:

I would like to know what is your tungsten carbide (WC + 17%Co) macrohardness (rockwell) range? Mine is around 91HRC in average. The reason to ask is to check if I could make it higher so to achieve better CpK reading under GE requirement.

Or you could share with me how to to increase it...

Thank you
ykang

[Simon Kim]

Is it HRN?

HRC is used under HRC70.

Simon

[loriolo]

Hi
Usually in thermal spray applications, they use to measure MACROHARDNESS, that is only as reference value, only to have an idea of the hardness of the coating, and this value for Wc17%Co is about 65 to 72 HRc, it depend of the system or parameters been used, to obtain this values you must use an HVOF system
To determine Microhardness value, that is quite the real hardness value of the coating, HR15N is used and this value for Wc__Co coatings can be around 90, some times is used Hv0.3, so Rockwell is used for Macrohardness measures and Vickers is used for microhardness .
Regards
Luigi

[Gordon]

Hi Ykang

HRC (Rockwell C scale) is not a suitable test for these coatings. Some quote HRC values as a guide because many are more familiar with scale. To do so requires conversion/equivalents from a practical test method. In the case of tungsten carbide coatings HRC equivalents are very hit and miss and meaningless. As said by Luigi, it seems 91 seems to be a realistic value for HR15N Rockwell superficial scale, but not HRC.

If you are considering increasing hardness, you need to be cautious. Harder WC /17%Co coatings are not necessarily better coatings Harder coatings can sometimes be the result of matrix hardening as a posed to increased density. This tends to be detrimental to the coating reducing ductility and abrasive wear resistance. I think there are some threads on the forum that discuss this in more detail.

Your hardness checking procedure may well be a factor in improving your CpK reading under GE requirement.

[ykang]

Dear All:

My mistake...It should be 91HR15N..Not HRC...