Application of cutting tools in heat-strength alloys

Application of cutting tools in heat-strength alloys

Aerospace processing is also changing rapidly. For example, nickel-based superalloys such as Rene88, which most people have not heard of a few years ago, now account for 10-25% of the total metal used in aeroengine manufacturing. There are good performance and business reasons for this. For example, these heat-strength alloys can increase engine life and allow smaller engines to work on large aircraft, which will increase combustion efficiency and reduce operating costs. These tough materials also show the cost on the tool. Their heat resistance leads to higher temperatures on the tool tip, which reduces tool life. Similarly, the carbide particles in these alloys significantly increase friction, thereby shortening tool life.

As a result of these changes in conditions, the cemented carbide material C-2, which used to be able to process many titanium alloys and nickel-based alloys satisfactorily, suffered severe crushing of the cutting edge and severe cut depth lines when applied to today’s alloys. The grooves are worn. However, the latest fine-grained cemented carbide can effectively process high-temperature alloys, and the tool life is improved, and more importantly, the reliability in the application of high-temperature alloys.

Fine-grain cemented carbide has higher compressive strength and hardness than traditional cemented carbide materials, but it adds a small amount of cost in terms of toughness. The result is that it is more effective than traditional cemented carbide in resisting common failure modes in high-temperature alloy processing.

PVD (Physical Vapor Deposition) coatings have also been proven effective for processing high-temperature alloys. TiN (Titanium Nitride) PVD coating was the first to be used and is still the most popular. Recently, TiAlN (titanium aluminum nitride) and TiCN (titanium carbonitride) coatings can also be used well. In the past, the application range of TiAlN coatings was more limited than TiN. But when the cutting speed increases, they are a good choice, increasing productivity by up to 40% in those applications. On the other hand, depending on the surface conditions of the coating, TiAlN at lower cutting speeds can cause built-up edge, subsequent chipping and groove wear.

Recently, materials for superalloy applications have been developed, and these coatings are composed of several layers. Extensive laboratory and field tests have demonstrated that this combination is effective in a wide range of applications compared to any other single coating. Therefore, the PVD composite coating for high-temperature alloy applications may become the continuous focus of the research and development of new cemented carbide materials. Together with MTCVD coatings and coated ceramics, they are expected to become the main impact force for more effective processing of new and more difficult-to-machine workpiece materials that are being developed.