Coated Cemented Carbide Types——Single-layer Coating

Since coated cemented carbide developed, coating types were diverse, such as single-layer coating, multi-element composite coating, gradient coating, nano coating, super-hard coating and soft coating.

1. Single-layer and multi-element composite coating

At present, titanium nitride (TiN) and titanium carbide (TiC) are the earliest and the most widely used, which has high hardness, excellent wear resistance. However, it is unavoidable that a big difference of modulus of elasticity and coefficient of thermal expansion between the matrix and the coating layer, which will decrease the binding force and residual stresses between them. In order to improve the comprehensive properties of tungsten carbide, adding some different kinds of elements to form multi-element coating layer. Ti (C,N) and TiAlN are the most common composite coating. In addition, there are some other elements can remarkably improve the properties of coating cemented carbide, such as Si element will increase the hardness and in case of the chemical diffusion, Zr, B, V and Hf elements will improve the wear resistance of material, Cr element will improve antioxidant property.

Take Ti (C,N) as an example, it has both of TiC and TiN coating advantages, which used in tungsten carbide cutting tools will remarkably improve the hardness and toughness, prevent the internal cracks diffusion and the tipping of tools. For coating layer, it decreases the inner stress and improves the binding force between coating layer and matrix. According to the consequence of turning experiment, compared with single-layer coating (TiC, TiN, Al₂O₃), composite coating layer Ti (C,N) has better tool face wear resistance and crater wear resistance, which is more suitable for common steel, alloy steel, stainless steel and iron casting machining by tungsten carbide cutting tools and the efficiency will be remarkably improved.

TiAlN composite coating layer has heat hardness and excellent antioxidant property and can be widely used in high-speed tungsten carbide cutting tools and cermet cutting tools. It mainly uses cathodic arc ion plating – physical vapor deposition, which has uniform structure, high density, high toughness, high micro hardness (increase 35%-76%) and suitable for high-speed steel, alloy steel and other high-performance materials high-speed milling and the service life is 3-4 times than TiN single-layer coating.

• < Prev
• Next >