With a melting point of 4,000F, which is the highest of all materials, diamond still has thermal limitations in many grinding applications:
- Diamond will start to oxidize above 600F into carbon-dioxide.
- Diamond has a tendency to react with ferrous metals (iron, cobalt, and nickel and its alloys) at a temperature above 700F
In light of this, diamond cannot be used to grind steel or titanium alloys if the temperature exceeds 700F. This makes it impossible for synthetic diamond to be used for the most common grinding applications, such as the grinding of hardened steel parts. This high rate of wear would make diamond uneconomical in comparison to CBN.
The biggest advantage of diamond is its high thermal conductivity (five times greater than copper). This high thermal conductivity allows diamond to transfer most of the heat away from the cutting edge and dissipate the thermal energy through the grinding wheel body into the grinding coolant, which hits the grinding wheel at a high flow rate.
This makes diamond the top-choice superabrasive for any material which is not soluble in carbon (non-metal materials). These include non-ferrous metal grinding (copper or aluminum alloys); cermets of ceramic (cemented tungsten-carbide, metal matrix composite Al-Si-C); and glass, silicon, granite, or marble.