Vacuum deposition utilizes the principle of metal volatilization. Under vacuum conditions, it employs methods such as micro-evaporation and sputtering to cause the metal atoms of the strong carbide-forming elements to reach the diamond surface through the gas phase process and deposit firmly on it. The metal atoms react with the carbon on the diamond surface to form stable carbides. The ideal coating for vacuum deposition should be: diamond – carbide – the metal or alloy to be deposited.
If necessary, another layer of metal or alloy can be vacuum-deposited or electro-deposited onto the coating to facilitate the infiltration and bonding of the tire body.
The current types of vacuum deposition include: Ti, Cr, W, Mo, etc., as well as their composite coatings. The ideal coatings are: Dia-TiC-Ti, Dia-Cr3C2-Cr7C3-Cr, Dia-WC-W2C-W, Dia-MoC-Mo2C-Mo.
Vacuum micro-evaporation deposition is currently one of the methods for depositing strong carbides with carbon-forming elements on diamond, and forming good chemical bonds. The temperature during the deposition of Ti can be controlled at around 650℃, which can effectively protect the diamond and achieve surface deposition of diamond powder as fine as 5 µm.
It should be noted that many methods of diamond coating still have certain problems, such as uneven coating, incomplete coating, inability to coat fine powders, excessively high coating temperature, and weak bonding between the coating and the diamond surface. These issues need to be further improved.