Carbide Coatings

Carbide Coatings is a kind of thin film coating method.

It refers to coating a surface of a cemented carbide insert with a wear-resistant TiC or a thin layer of TiN, HfN, Al2O3 or the like by chemical vapor deposition (CVD) to form a surface-coated cemented carbide.

After 1970, the United States, Japan and other countries began to produce such blades.

Over the past 30 years, thin film coating technology has made great progress. Coated cemented carbide inserts have been developed from the first generation to the second generation and the fourth generation.
Advantages of Carbide Coatings:

Coated carbide inserts are generally made into indexable styles. Use the machine clamp method to install the card on the tool holder or the tool body. It has the following advantages:

1) Since the coating material of the surface layer has extremely high hardness and wear resistance, the coated cemented carbide allows a higher cutting speed than the uncoated cemented carbide, thereby improving the processing efficiency; Significantly improved tool durability at the same cutting speed.

2) Since the coefficient of friction between the coating material and the material to be processed is small, the cutting force of the coated blade is somewhat reduced as compared with the uncoated blade.

3) When the coated blade is processed, the processed surface quality is good.

4) Due to the comprehensive performance, the coated blades have better versatility. A coated grade of blade has a wide range of applications.

The most common method for cemented carbide coating is high temperature chemical vapor deposition (HTCVD), which is a pure H2, CH4, N2, TiCl4, AlCl3, CO2 or other gas in a normal or negative pressure deposition system.

Vapor, according to the composition of the sediment, the relevant gases are uniformly mixed according to a certain ratio, and sequentially applied to the surface of the cemented carbide blade at a certain temperature (generally 1000 ° C ~ 1050 ° C), that is, depositing TiC, TiN on the surface of the blade , Ti(C,N) or Al2O3 or their composite coating.

Before coating, the surface of the base blade shall be cleaned and the cutting edge shall be passivated.

After the coating, there is a difference in the coefficient of linear expansion between the coating material and the base material, so that the surface of the coating blade inevitably generates residual tensile stress and the bending strength of the blade is lowered.

Usually, a thin layer of TiC is first applied on the surface of the substrate because the coefficient of linear expansion of TiC is closest to that of the substrate; TiN, Al2O3, etc. are coated on the outside. In the past, TiC was used for single-coat materials, TiC/TiN, TiC/Al2O3 for double-layer coating materials, and TiC/Ti(C,N)/TiN, Tic/Al2O3/TiN, etc. for the three-layer coating materials. In recent years, with the improvement of the matrix material, the coating material also has a TiN bottom, that is, a coating material such as TiN/TiC/TiN, and HfN, MoS2, and the like.