Ceramic end mills help optimize aerospace component machining
With components made from nickel-based alloys becoming increasingly prevalent across the aerospace industry, the demand for optimized cutting tools continues to grow. For common operations such as shoulder and face milling, machining nickel-based materials remains challenging. While offering excellent performances, these materials exhibit poor machinability due to their low thermal conductivity, the potential for adhering to cutting tools and the presence of abrasive particles within the alloy structure.
Due to these issues, productivity with carbide tools tends to be low. In addition, part complexity means that some components demand extended reach, while process flexibility is another factor high on the wish list of many aerospace manufacturers. Here, new ceramic end mill technology has emerged to help meet these requirements, offering the potential to optimize the machining of aeroengine parts and secure a significant competitive advantage.
Those tasked with producing aerospace engine components face many challenges. Most parts are manufactured from HRSAs/nickel-based alloys, which place particular demands on production engineers looking to manufacture components such as spools, turbine disks, combustion casings and blisks.
Up to 30 times faster
Although many manufacturers use conventional solid carbide end mills, such tools have their limitations in terms of performance when it comes to nickel-based alloys. In a highly competitive global arena, aerospace machine shops are looking for next-level technologies capable of delivering a step change in factors such as productivity and/or tool life. Ceramic end mills can provide that very leap, offering up to 20-30 times higher machining speed in comparison with solid carbide tools for operations such as shoulder and face milling. Such impressive gains can be achieved largely because ceramic cutters retain their hardness at the high temperatures experienced when machining nickel-based alloys.
The brazed ceramic CoroMill® 316 exchangeable-head end mill for roughing operations is a productive solution for aerospace engine applications in ISO S materials. Firstly, the exchangeable head concept facilitates inherent process flexibility. The range comprises a six-flute version with a straight corner radius that delivers highly productive side milling operations, and a four-flute version designed to boost face milling thanks to its high-feed face geometry.
The brazed ceramic CoroMill 316 end mill is ideal in difficult reachability conditions and offers the flexibility of the exchangeable head system.
The ceramic substrate of the end mills enables a different cutting process compared to traditional solid carbide tools. Importantly, the unique S1KU SiAlON grade is purpose-designed for superior machining of nickel alloys, and is supported by negative geometry that offers a tough cutting edge. The latter also features a T land for stable operations.
SiAlON has a chemical composition of aluminum oxide and silicon nitride (Al203+Si3N4), a combination that promotes high wear resistance, even at elevated temperatures.
Stable machining
A stable set-up is advised in all cases, and always without coolant application. Machine shops should use pressurized air instead, as coolant would simply burn up at the high temperatures involved. In addition, the use of coolant promotes thermal shocks and has a negative effect on tool life. Importantly, high spindle speeds of at least 13,000 rpm are required. Further recommendations include the use of down milling, as well as a programmed tool path that keeps the tool in constant contact with the material.
Good chip evacuation
A high cutting speed increases the cutting temperature, resulting in highly sheared chips. In fact, the process generates dust-like chips, which is good for chip evacuation using pressurized air.
Ceramic end mills retain their hardness at the high temperatures experienced when machining HRSA materials, making them especially suitable for blade machining of aerospace blisks.
No white layer
Notably, no white layer formation was observed when using ceramic end mills from Sandvik Coromant. Tests have been conducted for a wide range of cutting speeds between 375 and 900 m/min (1230 to 2953 ft/min) without any evidence of this unwanted effect. The white layer, which is thought to encourage cracks, is associated with the temperature increase at the surface of a workpiece followed by quick cooling.
In addition to shoulder milling and face milling, ceramic end mills can also be used for pocket milling, helical interpolation, ramping and slot milling. The CoroMill 316 is part of the Sandvik Coromant Optimized solutions offering within its solid round tools range.
The CoroMill 316 Ceramic ball nose end mill has a brazed ceramic on carbide interface which offers both strength and flexibility. The ball nose geometry ensures easier, faster profiling.
The series also includes a ceramic ball nose version of the CoroMill 316 for blisk machining. This profile milling solution is suitable for both roughing and finishing operations.
