The Basic Coatings Types of End Mill

The carbide end mill is also known as a cemented carbide end mill. The hardness of the tool itself is generally between HRA88-96 degrees. But with a coating on the surface, the difference comes. The cheapest way to improve the performance of an end mill is to add the right coating. It can extend tool life and performance.

What are the basic coatings of end mills on the market?

1. TiN - Titanium Nitride - basic general-purpose wear-resistant coating

TiN is the most common wear and abrasion-resistant hard coating. It decreases friction, increases chemical and temperature stability, and decreases sticking of material often occurring during machining of soft steels. TiN is suitable for coating tools made of cemented carbides– drill bits, milling cutters, cutting tool inserts, taps, reamers, punch knives, cutting tools, shear and flexion tools, matrices, and forms. Since it is biocompatible, it can be used on medical instruments (surgical and dental) and implantable devices. Due to its golden color tone, TiN has found wide use also as a decorative coating. The used TiN coating is easily stripped from tool steels. The reconditioning of tools can considerably decrease costs, especially when using expensive tooling.

2.TiCN – Titanium Carbo-Nitride – wear-resistant coating against adhesive corrosion

TiCN is an excellent all-purpose coating. TiCN is harder and more impact resistant than TiN. It can be used to coat cutting tools, punching and forming tools, injection mold components, and other wear components. Since it is biocompatible, it can be used on medical instruments and implantable devices. The machining speed can be increased and tool life can be enhanced by as much as 8x in the dependence on the application, coolant, and other machining conditions. The TiCN coating is recommended to be used for sufficiently cooled cutting due to its relatively lower thermal stability. The used TiCN coating is easily stripped and the tool recoated. The reconditioning of expensive tools can thus considerably decrease costs.

3. AlTiN-The Aluminium-Titanium-Nitride coating () 

It is a chemical compound of the three elements aluminum, titanium, and nitrogen. The coating thickness is between 1-4 micrometers (μm).

The special feature of the AlTiN coating is highly resistant to heat and oxidation. This is partly due to the nano hardness of 38 Gigapascal (GPa). As a result, it follows that the coating system despite a higher cutting speed and a higher cutting temperature remains stable. Compared to uncoated tools, AlTiN coating, depending on the application, increase an up to fourteen times longer service life.

The highly aluminum-containing coating is very well suited for precision tools, that cut hard materials like steel (N/mm²)<1,300, stainless steel, and cast iron.

The maximum application temperature is 900° Celcius (approx. 1,650° Fahrenheit) and compares to the TiN coating with a 300° Celcius higher resistance to heat.

Cooling is not mandatory. In general, cooling additionally increases the service life of the tool.

As mentioned in TiAlN coating, it should be noted that both the coating and the tool steel must be suitable for the application in hard materials. That's why we have coated special drills made of tungsten-carbide with AlTiN.

4.TiAlN – Titanium Aluminum Nitride – wear-resistant coating for high-speed cutting

TiAlN is a coating with excellent hardness and high thermal and oxidation resistance. The incorporation of aluminum increased the thermal resistance of this composite PVD coating with respect to the standard TiN coating by 100°C. TiAlN is typically coated on high-speed cutting tools used on CNC machines for machining materials of higher toughness and at severe cutting conditions. TiAlN is suitable especially for monolithic hard metal milling cutters, drill bits, cutting tool inserts, and shaping knives. It can be used in dry or near-dry machining applications.

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