How to improve the life of cemented carbide CNC inserts

Cutting Tools have very wide application in the machine industry, but its shortage is consume very fast, so we study of tools life has never stopped. The life of the tools usually depends on the material of the tools. the workpiece processed and the different processing technology, so the life of the tools needs to be determined according to the specific situation. Now let's discuss how to improve the life of Cemented Carbide CNC inserts.

Evolving tool matrix, coating, and cutting edge preparation technologies are essential to limit tools wear and resist high cutting temperatures. These elements, with the chip slot and corner arc radius used on the indexable inserts, it determine the suitability of each tools for different parts and cutting processes. All of these elements extend tool life, making the cutting process more economical and reliable.

We have summarized three method to improve the cutting life:

1. Change the matrix

By varying the size of tungsten carbide in the range of 1-5μm, we can vary the matrix properties of cemented carbide tools. The particle size of matrix material plays an important role in cutting performance and tool life. The particle size is smaller, the abrasion resistance of the tools is better. On the contrary, the particle size is larger, the tools strength and toughness is better.

In addition, increasing the cobalt content of carbide CNC inserts materials by 6-12% leads to better toughness. Therefore, cobalt content can be adjusted to meet specific cutting requirements, whether such requirements are toughness or wear resistance.

The properties of the tool matrix can also be enhanced by the formation of a cobalt-rich layer close to the outer surface, or by the selective addition of other alloying elements such as titanium, tantalum, vanadium, and niobium to the cemented carbide material. Cobalt-rich layers can significantly improve cutting edge strength, thereby improving the performance of rough and discontinuous cutting tools.

When we selecting the tools matrix that matches the workpiece material and processing mode, we also should consider other five matrix properties -- fracture toughness, transverse fracture strength, compressive strength, hardness and thermal impact resistance. For example, if the carbide tool breaks along the cutting edge, the matrix material with higher fracture toughness should be selected. In the case of direct cutting edge failure or breakage, the possible solution is to choose a matrix material with higher transverse fracture strength or higher compressive strength. For high cutting temperature processing occasions (such as dry cutting), usually should choose higher hardness of the tool material. In machining situations where thermal cracking of the cutting tool can be observed (common in milling), it is recommended to choose the cutting tool material with better thermal impact performance.

2. coating selection

The coating also helps to improve the cutting performance of CNC carbide inserts. The coating technologies include:

① Titanium nitride (TiN) coating: This is a universal PVD and CVD coating, which can improve the hardness and oxidation temperature of the tool.

(2) Titanium carbon nitride (TiCN) coating: by adding carbon element in TiN, the hardness and surface finish of the coating are improved.

(3) Nitrogen aluminum titanium (TiAlN) and nitrogen titanium aluminum (AlTiN) coating: alumina (Al2O3) layer and the composite application of these coatings can improve the tool life of high temperature machining. Alumina coatings are particularly suitable for dry and near dry cutting. The AlTiN coating has a higher aluminum content and has a higher surface hardness than the TiAlN coating with a higher titanium content. AlTiN coatings are commonly used in high speed machining. Tungsten steel aseismic turning tool bar

(4) Chromium nitride (CrN) coating: This coating has good adhesion resistance, is the solution to fight against the chip tumor.

(5) Diamond coating: diamond coating can significantly improve the cutting performance of non-ferrous materials tool processing, very suitable for processing graphite, metal matrix composites, high silicon aluminum alloy and other high abrasive materials. However, diamond coating is not suitable for processing steel parts, because its chemical reaction with steel will destroy the adhesion property of coating and substrate.

3. Preparation of cutting edge

In many cases, the preparation of inserts cutting edge (or blade passivation) has become the watershed that determines the success or failure of machining. Passivation process parameters should be determined according to specific processing requirements. For example, blades used for high speed finishing steel parts have different requirements for blade passivation than blades used for rough machining. Blade passivation can be used to process almost any type of carbon steel or alloy steel blade, but in the process of stainless steel and special alloy materials, its application is limited. The amount of passivation can be as small as 0.007mm or as large as 0.05mm. In order to enhance the cutting edge in poor machining conditions, it can also form a small T-shaped edge band by cutting edge passivation.

In general, blades used for continuous turning and milling most steel and cast iron require a large degree of edge passivation. The amount of passivation depends on the carbide grade and the type of coating (CVD or PCD coating). For heavy discontinuous cutting blades, it has become a prerequisite to passivate the cutting edge severely or to produce T-shaped ribs. Depending on the coating type, the amount of passivation can be close to 0.05mm.

In contrast, since the blades used to process stainless steel and superalloys are prone to chip nodules, the cutting edges are required to be sharp and can only be slightly passivated (as small as 0.01mm), and even smaller passivations can be customized. Similarly, the blades used to process aluminum alloys are required to have sharp cutting edges.

To improve the service life of the tool, in addition to the above three points, in the usual processing time also should pay attention to the correct use of the knife, whether machine plus or manual processing, in the use of the tool to operate in strict accordance with the specification. Reasonable use of the knife can also improve the service life of the tool, reduce the investment in the tool.