High-end coatings for reliable and cost-effective machining of complex Aerospace components made from difficult-to-cut materials

Machining operations for the aerospace sector are tough. Learn more about Ionbond’s Tetrabond™ Plus and Hardcut™ Plus coatings, developed for machining complex components and hard-to-machine materials.

The aerospace industry is continuously evolving, with increasing demands to reduce fuel consumption and emissions, while maintaining high safety, reliability and high structural efficiency. Aerospace structural materials require high strength and stiffness, low weight, high thermal stability, and high corrosion and oxidation resistance. As a result, aluminum alloys, titanium alloys, super-alloys, and composites are the most commonly used materials for aerospace structures.

However, these materials are extremely challenging to machine: the cutting tool experiences extensive wear under severe operating conditions, ranging from high temperatures to heavy mechanical loads. Ionbond offers environmentally friendly coating solutions that fulfill the requirements for machining of various aerospace structural materials and considerably improve the performance and cost-effectiveness of the cutting tools.

Ionbond Plus coatings, approved by the aerospace industry, exhibit a tailored microstructure and the quality and properties to improve the tool performance while machining of difficult-to-cut materials.

Challenges in machining aluminum alloys

Aluminum alloys used for aerospace components are difficult to machine due to their high ductility and low melting temperatures. Aluminum has the tendency to stick to the cutting edge, resulting in built-up material which leads to high friction and wear during machining. In addition, high-alloyed aluminum is highly abrasive, which also limits the tool life.

Ionbond has developed the Tetrabond™ Plus coating for this application. It possesses extremely high hardness and low affinity towards aluminum alloys. Tetrabond^™ Plus is an advanced ta-C (tetrahedral carbon) coating with a sp3 content of 60 – 70% and a hardness of over 5000 HV. The thin, smooth, and extremely hard coating is designed to maintain maximum cutting edge sharpness, a prerequisite for machining aluminum alloys. Its high hardness, high thermal stability, very low coefficient of friction, and anti-sticking properties make Tetrabond^™ Plus excellent at suppressing the formation of built-up material on the cutting edge and thus results in considerable improvement of tool lifetime during machining of aluminum alloys.

Tools coated with Tetrabond™ Plus

Tetrabond^™ Plus:

High sp³ content for extremely high hardness and exceptional wear resistance
Extremely dense microstructure and smooth surface
Very low coefficient of friction
Very low sticking tendency towards aluminum alloys
Very thin coating (approx. 0.5µm), ensuring that the cutting edges remain sharp

By virtue of its extremely high hardness, a thick Tetrabond^™ Plus coating (approx. 3.0 – 4.0 µm) can be used as alternative to chemical vapor deposition (CVD) diamond coatings for machining carbon-fiber-reinforced polymer composite materials used in the aerospace industry.

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Challenges in machining titanium alloys and super-alloys

Titanium is one of the fastest growing materials used in aerospace applications, due to its relatively low mass for a given strength level and its high thermal stability. Super-alloys show high temperature corrosion resistance, oxidation resistance and creep resistance and thus are also widely used in aerospace components.

Machining of these alloys is demanding due to the high chemical reactivity of titanium alloys. This causes the chip to weld to the cutting edge, leading to galling and premature tool failure. Another challenge is that the low thermal conductivity of these alloys does not allow the heat generated during machining to dissipate from the tool edge, leading to excessive tool deformation and wear. The high work-hardening tendency of these alloys leads to higher cutting forces and high temperatures at the cutting edge. In addition, hard, abrasive intermetallic compounds in the super-alloys causes severe abrasive wear of the tool.

Ionbond’s Hardcut™ Plus coating is engineered for machining these materials, protecting the cutting tool at high machining temperature. The coating is thermally stable at an operating temperature of up to 1100 °C. A distinguishing feature of Hardcut^™ Plus is its optimized microstructure: a multi-layer coating with a nanocomposite outer layer with TiN nanocrystallites in an amorphous Si₃N₄ matrix.

Tools coated with Hardcut™ Plus

Hardcut^™ Plus exhibits high chemical inertness, extremely high hot hardness, very low thermal conductivity and very high oxidation resistance. These properties improve tool life while machining titanium and super-alloys, by suppressing adhesion wear, providing excellent abrasion wear resistance and acting as thermal barrier to protect the tool material. This is how Hardcut^™ Plus allows coated tools to sustain high temperatures and show no excessive wear at the cutting edge.

Hardcut^™ Plus:

Optimized multilayer architecture with nanocomposite top layer
High hot hardness and exceptional wear resistance
Superior thermal stability, oxidation resistance and chemical inertness
Very low thermal conductivity, protecting the tool at high cutting temperatures
Extremely smooth surface

Are you interested in learning more about our Plus coatings?

Both Plus coatings, Tetrabond™ Plus and Hardcut™ Plus, can be applied to HSS, cemented carbide and brazed tools, regardless of geometry. Tools with these coatings can be resharpened and recoated to make the best use of expensive cutting tools.

Are you interested in learning more about Ionbond’s Plus coatings for aerospace applications? Come find us at the Farnborough International Airshow (FIA) from 18-22 July at booth 4230 in hall 4 or contact Dr. Kalpak Shaha by filling in the contact form.