METHOD FOR FORMING COMPLEX FILM OF DIAMOND-LIKE CARBON AND SILICON CARBIDE

A method for applying a resin-repellant coating to an injection molding component made of metal forms a complex film of diamond-like carbon (DLC) and silicon carbide (SiC) on the metal. A vacuum chamber is evacuated of air and an electric field is created in the chamber. A first gas containing carbon and a second gas containing silicon interact with an ionized noble gas as a working gas in the chamber. A first film of SiC is deposited and bonded on the metal die, a second film of DLC from excess carbon atoms is then deposited and bonded on the first film to form the complex film.

DETAILED DESCRIPTION

The figure shows a chamber20for implementing an embodiment of a method for forming complex film of diamond-like carbon and silicon carbide (SiC). A power supply30is located in the chamber20.

The power supply30is switched on to create an electric field in the chamber20. The electric field can drive a working gas to move in a high speed and form a plasma within the electric field. The working gas generally is a noble gas, for example, hydrogen, argon, or helium. The power supply30can be a direct current power supply, radio-frequency (RF) power supply, or microwave power supply.

A first opening21, a second opening22, and a third opening23are defined on a same side or different sides of the chamber20. One of the first opening21, the second opening22, and the third opening23is an exit for gases. The other two openings are entrances for gases.

Steps of the method for forming complex film are as follows.

One or more metal workpieces10are cleaned and then placed into the chamber20.

Air in the chamber20is evacuated through the first opening21. After gas evacuation, air pressure in the chamber20is between 10−3torr and 10−5torr.

A first gas containing carbon element is applied into the chamber20through the second opening22and a second gas containing silicon element is applied into the chamber20through the third opening23. The working gas is applied into the chamber20together with the first gas or together with the second gas.

The ratios by volume of the first gas, the second gas, and the working gas are 100:5:1 respectively. In other words, 100 parts of the first gas, 5 parts of the second gas, and one part of the working gas are applied into the chamber20.

The first gas can be methane or ethyne. The second gas can be hexamethyldisiloxane (HMDSO) or silane.

Under the electric field in the chamber20, the working gas in the chamber20is accelerated to high speed. The working gas strikes the first gas and the second gas, and ionizes both the first gas and the second gas. Carbon ions and silicon ions are separated from the first gas and the second gas respectively. The number of the carbon ions is greater than that of the silicon ions. A chemical reaction between the carbon ions and the silicon ions occurs and silicon carbide is produced. The silicon carbide is deposited on the metal workpiece10. The excess of carbon ions is deposited onto the metal workpiece10to form diamond-like carbon and thus a complex film11of diamond-like carbon and silicon carbide is formed on the metal workpiece10.

The silicon element content makes that the water contact angle (liquid-repelling property) of the complex film11is larger than 100 degrees.

Thickness of the complex film11is 300 nanometers, friction coefficient of the complex film11is smaller than 0.01, hardness of the complex film11is 3000 Hv, and smoothness of the complex film11is smaller than 10 nanometers in variation.

Diamond-like carbon and silicon carbide integrates with each other and a good bond is created between the silicon carbide and the metal workpiece10, so the overall bonding of the complex film11to the metal workpiece10is enhanced.