Coating selection for end mills when processing hard materials

When processing hard materials, the selection of coating for end mills is of vital importance, as it directly affects the tool’s lifespan, processing efficiency and the surface quality of the workpiece. The following is a detailed analysis of the coating selection for end mills when processing hard materials:

First, common coating types and characteristics

Titanium nitride coating (TiN)

Features: Enhances tool hardness, has a relatively high oxidation temperature, and is suitable for high-speed cutting.

Applicable scenarios: It is often used in high-speed steel cutting tools or forming tools, and performs well when processing materials with low hardness.

Titanium nitride coating (TiCN)

Feature: The carbon element added to the coating can enhance the hardness of the cutting tool and achieve better surface lubricity.

Application scenarios: It is an ideal coating for high-speed steel cutting tools, especially suitable for processing occasions that require high wear resistance and lubricity.

Titanium aluminum nitride or titanium aluminum nitride coating (TiAlN/AlTiN) :

Feature: The aluminum oxide layer formed in the coating can effectively increase the service life of the cutting tool under high-temperature processing.

Application scenarios: Mainly used for hard alloy cutting tools in dry or semi-dry cutting processes, especially suitable for high-speed processing fields. Among them, the AlTiN coating, due to its higher proportion of aluminium, can provide a higher surface hardness than the TiAlN coating.

Diamond coating

Characteristics: It features extremely high hardness and excellent wear resistance, making it an ideal coating for processing non-ferrous metal materials.

Applicable scenarios: It is suitable for processing graphite, metal matrix composites (MMC), high-silicon aluminum alloys and highly abrasive materials. However, it should be noted that pure diamond-coated tools cannot be used to process steel parts, as a large amount of cutting heat is generated during the processing of steel parts, which causes the adhesion layer between the coating and the tool to be damaged.

Nitrogen-chromium aluminum coating (AlCrN)

Characteristics: It has excellent anti-adhesion properties and can prevent or mitigate chemical reactions between the cutting tool and the processed material.

Application scenarios: It is the preferred coating in processing where built-up edge is prone to occur, and can significantly improve the processing performance of high-speed steel, hard alloy and other cutting tools.

Second, suggestions for coating selection

Select according to the hardness of the processed material:

For materials with high hardness (such as quenched steel, high-temperature alloys, etc.), coatings with high hardness and good wear resistance, such as TiAlN/AlTiN or diamond coatings, should be selected.

For materials with slightly lower hardness (such as stainless steel, titanium alloy, etc.), TiCN or AlCrN coatings can be selected to balance the hardness and toughness of the cutting tool.

Select according to the processing conditions:

Under dry or semi-dry cutting conditions, coatings with good heat resistance and oxidation resistance, such as TiAlN/AlTiN, should be given priority.

In processing scenarios that require high lubricity, TiCN or composite coatings with soft coating characteristics can be selected.

Consider the compatibility between the coating and the tool substrate:

The coating should have good adhesion to the base material of the cutting tool to ensure that the coating is not prone to peeling off during the processing.

The thickness and composition of the coating should be optimized according to the specific application and processing requirements of the cutting tool.