
Kovar is a nickel-cobalt alloy, primarily composed of iron (approximately 29%), nickel (29%), and cobalt (17%), its thermal expansion coefficient is similar to that of glass, making it ideal for hermetic seals with glass in applications such as vacuum tubes, electronic tubes, and semiconductor devices. Among the various materials that can be machined using CNC technology, Kovar alloy stands out due to its unique properties and diverse applications.
CNC Machining Processes for Kovar
CNC machining of Kovar involves several key processes, each tailored to achieve precise specifications and high-quality finishes. Here’s an overview of the primary CNC machining techniques used for Kovar:
Turning
In CNC turning, the Kovar workpiece is rotated while a stationary cutting tool removes material. This method is ideal for creating cylindrical parts, including shafts and fittings. It allows for high precision and can produce complex geometries with smooth surface finishes.
Milling
CNC milling employs rotating cutting tools to remove material from a stationary Kovar workpiece. This technique enables the creation of complex shapes, features, and contours. It is highly versatile, suitable for various part geometries, including pockets, slots, and intricate designs.
Drilling
CNC drilling involves using a rotating drill bit to create holes in Kovar components. This is crucial for applications requiring precise mounting or assembly. High precision and repeatability ensure that holes meet specific tolerances, which is essential for the functionality of assembled parts.
Grinding
CNC grinding is used to achieve high tolerances and superior surface finishes. It involves removing material using a rotating grinding wheel, refining the part’s dimensions. This process is critical for achieving the exact specifications required in high-performance applications, ensuring parts meet stringent industry standards.
Considerations for CNC Machining Kovar
When machining Kovar alloy, several vital factors must be taken into account due to its unique properties.
- Coefficient of Thermal Expansion (CTE): When connecting Kovar with other materials, it’s essential to match the CTE of Kovar and adjacent materials to prevent mechanical and thermal stress during operation.
- Cutting Parameters: The choice of cutting parameters (feed rate, spindle speed, and depth of cut) is crucial. Typically, smaller feed rates and deeper cuts are employed to balance material removal rates with tool life and surface finish.
- Slower Speeds and Higher Feeds: Kovar’s toughness necessitates slower machining speeds and higher feed rates to minimize work hardening. Maintain consistent speeds for different diameter holes and ensure thorough cleaning to optimize conditions.
- Carbide Tools: Using carbide tools is advisable due to Kovar’s abrasive nature. Cemented carbide offers excellent tool life and durability compared to softer materials like high-speed steel. Handle carbide tools carefully to avoid chipping.
- Fixture Design: Proper fixture design ensures stable clamping of workpieces, minimizing vibrations and ensuring accurate machining. Special attention should be paid to fixture materials and clamping forces to avoid galling or deformation of the Kovar alloy.
- Pre- and Post-Annealing: Pre-anneal Kovar parts before machining to relieve stress and work hardening. Controlled post-annealing is also crucial for maintaining dimensional and mechanical stability.
- Finishing Treatments: Apply surface treatments to eliminate oxidation and contamination, enhancing the lifetime and solderability of Kovar parts.
Challenges and Solutions in CNC Kovar Machining
- Work Hardening: Kovar is prone to work hardening, complicating the machining process.Reduce drill speeds by half and maintain low overall cutting speeds. Ensure thorough lubrication to minimize heat generation and risks of hardening.
- Tool Wear: The toughness and abrasiveness of Kovar lead to increased tool wear. Use carbide or diamond-coated tools, which maintain sharpness and withstand the demands of machining Kovar.
- Thermal Expansion Management: Kovar’s controlled thermal expansion can be problematic if not managed properly. Plan machining processes with operating temperatures in mind to account for thermal expansion.
- Surface Oxidation: Heating Kovar can lead to oxide layer formation, affecting surface quality. Control the machining environment and speed to minimize heating, and consider post-machining treatments like passivation.
- Internal Stress: Improper annealing can lead to internal stresses in Kovar parts. Properly anneal parts before machining and consider additional annealing post-machining to stabilize components.

Applications of CNC Machined Kovar Parts
CNC machined Kovar components are utilized across various industries:
Electronics
CNC machined Kovar components are integral to the electronics industry, particularly in the production of vacuum tubes. Kovar forms a hermetic seal with glass, ensuring reliable performance in high-frequency applications. Additionally, it is used in electronic headers and packages, providing stable connections that are essential for efficient operation.
Aerospace
In the aerospace sector, Kovar’s unique properties make it ideal for sensor housings that must maintain dimensional stability under varying temperature conditions. This reliability is crucial for aircraft performance. Furthermore, Kovar is used in optical systems, where low thermal expansion is essential to maintain precise alignment of components.
Medical Devices
The medical field benefits from Kovar’s biocompatibility, making it suitable for implantable devices that require both durability and precision. CNC machined Kovar parts are also found in surgical instruments, where high accuracy and reliability are paramount for successful outcomes.
Telecommunications
Kovar’s stable electrical properties make it an excellent choice for components in telecommunications, particularly in radio frequency applications. Its reliability in connectors and other essential parts ensures optimal performance in high-frequency environments.
Automotive
In the automotive industry, Kovar is utilized in sealing components that need to perform reliably in harsh conditions. Its ability to maintain integrity contributes to the overall system reliability, making it a preferred material for various automotive applications.
Research and Development
CNC machined Kovar parts are also prominent in research settings, particularly in experimental equipment that requires precise temperature control and stability. This includes applications in cryogenics and other scientific studies, where the material’s unique properties are invaluable.
Comparing Kovar to Other Metals
Kovar alloy is distinguished by its low thermal expansion coefficient, making it suitable for applications requiring stability between metal and glass, unlike aluminum and steel, which have higher coefficients. It offers consistent magnetic properties, beneficial for electronic applications, while being tougher to machine than materials like aluminum and brass due to work hardening. Although Kovar provides good corrosion resistance, it is not as effective as stainless steel or titanium. Additionally, Kovar’s higher cost stems from its nickel and cobalt content, making it more expensive than common metals such as aluminum and copper.
Property | Kovar Alloy | Aluminum | Copper | Titanium | Stainless Steel |
---|---|---|---|---|---|
Composition | Fe-Ni-Co alloy | Al | Cu | Ti | Fe-Cr-Ni (varies) |
Color | Silver-gray | Silvery | Reddish-brown | Silvery | Silver-gray |
Thermal Expansion Coefficient (ppm/°C) | 4.6–5.4 (at 30°C) | 23.1 | 16.5 | 8.6 | 17.3 |
Machinability | Moderate (special tools) | High | High | Low | Moderate |
Magnetic Properties | Magnetic | Non-magnetic | Non-magnetic | Non-magnetic | Usually non-magnetic or slightly magnetic |
Corrosion Resistance | Good (better than carbon steel) | Excellent | Good | Excellent | Excellent |
Cost | Higher (contains Ni and Co) | Lower | Moderate | Higher | Moderate |
Case Study: High-Precision Kovar Machining
Consider the manufacturing of a precision Kovar component for an electronic device. The component requires intricate features and tight tolerances. By utilizing a state-of-the-art CNC machine equipped with high-performance tools and advanced software, manufacturers can achieve the required precision and complexity. The process involves:
- CAD/CAM Integration: Designing the component in CAD software and converting it to a machinable G-code program using CAM software.
- Machine Setup: Loading the Kovar workpiece into the CNC machine, selecting the appropriate tools, and setting the cutting parameters.
- Machining Execution: Running the G-code program, which controls the movements of the cutting tools to shape the Kovar workpiece.
- Quality Control: Inspecting the machined component for dimensional accuracy, surface finish, and feature integrity.
Conclusion: Choose BOYI for Your Machining Needs
By leveraging advanced CNC technology, manufacturers can achieve unparalleled precision, efficiency, and repeatability. Proper tool selection, cutting parameter optimization, and attention to detail throughout the process are essential to producing high-quality Kovar components that meet stringent specifications and performance requirements.
BOYI excels in Kovar alloy manufacturing, utilizing advanced CNC technology and specialized tooling to address the unique challenges of Kovar. With a focus on tight tolerances and exceptional surface finishes, BOYI ensures that every part meets or exceeds specifications.

Let’s Start A New Project Today
All information and uploads are secure and confidential.

This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.