Case Study: SDF End Mills for Composite Machining of Tube Sheet in Nuclear Power Heat Exchangers

Industry Background and Machining Challenges:

Nuclear power heat exchangers are critical components in energy equipment, used to transfer heat between two fluids in a sealed system. One of the most demanding machining tasks is the composite drilling and milling of the tube sheet, which typically requires high precision and surface finish. The tube sheets are often made of high-strength stainless steel or nickel-based alloys such as Inconel 625 or Incoloy 800, materials that are highly resistant to corrosion and thermal fatigue, but also notoriously difficult to machine due to their high hardness and low thermal conductivity.

The typical manufacturing process includes rough milling, finishing milling, and composite drilling. During these operations, manufacturers face a variety of challenges, including:

• High material hardness: These materials can range from 30 to 45 HRC, making chip formation and tool wear significant issues.
• Strict surface finish requirements: Surface roughness often needs to be within Ra 0.8 μm or less, requiring tools with exceptional edge control and cutting stability.
• Efficiency bottlenecks: Due to the high strength of the materials, conventional tools may not achieve sufficient metal removal rates, leading to long cycle times.
• Chip evacuation: The adiabatic cutting behavior of nickel-based alloys often leads to long, stringy chips, which can clog the cutting zone and reduce tool life.
• Vibration and chatter: The combination of high stiffness and low damping in these materials can result in tool deflection and chatter, especially during high-speed machining.

Technical Requirements for End Mills in This Industry:

For composite machining in the nuclear energy sector, the selection of end mills must meet several stringent technical requirements, including:

• Chip evacuation: Effective chip breaking and rapid evacuation to avoid tool clogging and thermal damage.
• Surface finish: Capability to maintain high-quality surface finish under high cutting speeds and feeds.
• Vibration control: Stable tool design to minimize deflection and chatter, especially in thin-walled or deep cavity applications.
• Tool wear resistance: Long tool life under high-temperature and high-stress cutting conditions.
• Chip control: Consistent and predictable chip formation for continuous and semi-continuous machining.
• Thermal stability: Maintaining tool geometry and performance at elevated cutting temperatures.
• Edge stability: Strong edge retention and resistance to chipping or cratering during high-load cutting.

SDF’s Product Solution:

SDF has developed a series of solid carbide end mills specifically for the composite machining of nuclear heat exchanger tube sheets. These tools combine advanced structural design, high-performance coating technologies, and premium carbide grades to deliver robust cutting performance and long tool life.

Structural Design:

• Helix angle optimized for deep cavity and composite drilling applications to improve chip evacuation and reduce cutting forces.
• Flute geometry designed with a variable pitch and variable helix to suppress vibration and chatter.
• Corner radius options and end cutting geometry allow for efficient ramping and profiling operations.

Coating Technology:

• Advanced multi-layer PVD coating system with AlCrN-based structure to provide high hardness and thermal resistance up to 900°C.
• Surface smoothness and reduced friction coefficient to enhance surface finish and reduce tool wear.

Material Selection:

• High-performance tungsten carbide substrate with micrograin structure to increase toughness and edge stability.
• Customized alloying elements for improved resistance to thermal shock and mechanical fatigue.

Below is a comparison of SDF end mills with tools from other leading international brands, based on key parameters and life testing in a typical nuclear heat exchanger application:

Typical Customer Application Case:

A major nuclear power equipment manufacturer in Europe faced significant challenges during the machining of a nickel-based alloy tube sheet (Inconel 625) for a heat exchanger. The existing end mill from a certain brand failed to meet the required surface finish and exhibited frequent edge chipping, resulting in high tooling costs and low production efficiency. The customer required a solution to improve tool life and reduce cycle time by 15% without compromising quality.

The SDF technical team conducted an in-depth analysis of the customer’s machining process and recommended a customized solid carbide end mill with a 5-flute design, micrograin substrate, and an advanced AlCrN coating. Tooling was tested in real production conditions at the customer’s site, and the results were compelling.

Conclusion and Brand Value Summary:

SDF has demonstrated strong technological capabilities in developing solid carbide end mills for the nuclear power heat exchanger industry. Through a combination of precision engineering, advanced coating systems, and high-performance materials, SDF tools effectively address the challenges of machining high-strength alloys while maintaining high surface quality and tool life. The case study highlights SDF’s ability to deliver cost-effective solutions that outperform international competitors in terms of tool longevity and machining efficiency.

The brand has positioned itself as a high-value alternative to foreign manufacturers, leveraging the advantages of localized support and competitive pricing without compromising on technical performance. As the energy equipment industry continues to evolve with higher material requirements and more complex geometries, SDF is well-positioned to support these advancements through continuous innovation and R&D investment. We are committed to providing cutting-edge tooling solutions that enhance productivity and reliability in critical applications.