Diamond coating temperatures can vary significantly depending on the process used.
What is the Temperature of Diamond Coating? 5 Key Points to Know
1. Chemical Vapor Deposition (CVD)
In CVD, the substrate temperature can reach between 800°C and 1051.6 °C (1472°F – 1925°F).
This temperature is higher than the tempering temperature of steel.
Most jewelry and watches made from materials with low melting points cannot withstand these high temperatures.
2. Physical Vapor Deposition (PVD)
In PVD, the average temperature is much lower, ranging from 70°C to 398.8°C (158°F – 750°F).
This temperature range is suitable for almost all materials, including plastics.
3. Thermal Expansion and Contraction
During the diamond deposition process, the substrate tends to expand and then contract back to its original lattice spacing at room temperature.
The diamond coating, with its very small thermal expansion coefficient, will be left relatively intact by the change in temperature.
This results in significant compressive stresses in the diamond coatings, potentially causing substrate bow, cracking, flaking, or even detachment of the entire film from the substrate surface.
4. Tool Material Selection
The proper selection of tool material is crucial for successful diamond coating.
The prolonged high temperature during the coating process can damage most materials, except for cemented tungsten-carbide and ceramic cutting tools.
For optimum coating adhesion, a C-2 grade of tungsten-carbide with a six percent cobalt binder and tungsten carbide grain size above one micron must be used.
5. Coating Process Preparation
The coating process itself involves careful preparation of the tools before diamond coating.
The parts are cleaned and undergo a two-step chemical preparation to roughen the carbide surface for improved mechanical adhesion and remove cobalt, which is poison to diamond growth.
The parts are then loaded into a chamber containing hydrogen and methane gases.
Tungsten wires heated to over 2,300°C (4,172°F) are used to break up the gas molecules and heat the tools to over 750°C (1,382°F).
Under the proper conditions, activated carbon atoms recombine into crystal carbon and grow together to form a pure diamond film over the entire tool surface.
Continue exploring, consult our experts
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