Kovar Alloy Machining: Top Applications and Why You Should Choose It

What is Kovar Alloy: A Nickel Iron Cobalt Alloy

Kovar alloy is a silver-gray metal invented in the early 20th century. It is made predominantly of iron, nickel, and cobalt. Kovar has a particularly low thermal expansion coefficient, the same as glass and ceramics. This characteristic makes it possible to make reliable hermetic seals. Kovar has been an essential tool for manufacturing parts of superior quality and tight tolerances in the electronics, aerospace, and medical industries.

Comparing Kovar Alloy to Other Metals

Each metal has a unique combination of attributes, suitable for a wide range of applications.

Thermal Expansion: Kovar alloy’s low thermal expansion coefficient allows it to behave similarly to that of borosilicate glass or ceramics. This makes it distinct from metals like steel or aluminum with vastly different coefficients.

Magnetic Properties: While metals like stainless steel can be nonmagnetic, Kovar offers consistent magnetic properties important for many electronic applications.

Machinability: Kovar is tougher to work with than typical aluminum or brass materials since it work hardens. However, it can be machined to tight tolerances with the correct machinery and machining process.

Corrosion Resistance: It provides better corrosion resistance than carbon steels. However, the corrosion resistance for Kovar is not comparable to stainless steel or titanium.

Cost: Due to the special applications and alloy counterparts of nickel and cobalt materials, it is often more expensive compared to more common metals like aluminum or steel materials.

Common Machining Types and Cutting Tools for Kovar Alloy

Kovar alloy’s tough material properties necessitate specific machining processes to achieve precision components. High-speed tools are essential for operations like cutting, turning, drilling, reaming, and tapping, with heat control being crucial to prevent material warpage. Here are some common machining methods for Kovar:

Tool Requirements

Utilizing sharp tools with proper edge treatments is vital for effective machining. Removing feathered or wire edges from tools ensures their optimal performance and longevity. Optimized cutting edge angles, particularly end cutting edge angles greater than 25°, are recommended for efficient cutting.

CNC Machining

CNC machining is a robust method for producing high-quality, repeatable Kovar parts. The use of high-speed, sharp tools with precise edge treatments is key to achieving superior surface finishes. Steel tools with optimized cutting edge angles effectively shape intricate designs, crucial due to Kovar’s tendency to work harden. CNC machining’s precision and automation ensure consistency, material economy, reduced post-processing, and timely production, making it indispensable in aerospace and electronics industries.

Electric Discharge Machining (EDM)

EDM excels in shaping heat-resistant Kovar, fabricating intricate designs with dimensional precision. As a non-contact technique, it avoids mechanical stress, preserving material integrity. EDM controls thermal impact, prevents tool wear, and delivers fine tolerances and finishes, often eliminating the need for post-processing. Its capability to produce complex shapes and etched details without altering geometry is crucial in precision-dependent industries like aerospace and electronics. For tapping, using a slightly larger tap drill and a fluted tapping tool maintains thread integrity.

Laser Cutting

Laser cutting is effective for Kovar alloy, using a focused beam to yield precise cuts with clean edges. This technique offers high repeatability for complex shapes and is both fast and efficient. It minimizes material waste, reduces tool wear, and maintains a small heat-affected zone, preventing property changes in the material. Laser cutting is ideal for intricate designs requiring precision and speed.

Key Applications of Kovar Alloy Machining

Glass Sealing: Kovar material is machined into components for glass-to-metal seals in vacuum systems. The coefficient of thermal expansion, CTE, of this alloy matches that of borosilicate glass and other ceramics.

Electronics: The Kovar material is used for diodes, transistors, and other electrical parts with semiconductive features. Kovar’s high mechanical strength and electrical conductivity provide reliable connections between ceramic and copper or alloy parts.

Aerospace: Kovar alloy machining is a suitable process for aerospace components that operate under changing temperature environments and have tight sealing requirements.

Telecommunications: Kovar’s precision-machining process provides the essential parts for satellite and radio systems due to its dimensional stability and thermal expansion matching requirements.

Instrumentation: Precision machining Kovar material parts serve scientific instruments that operate across different temperature variations.

Medical Devices: Machining Kovar metal parts are compatible with the medical industry’s need for biocompatible instruments and temperature-consistent implantable devices.

Kovar parts features when machining metal parts for applications requiring matching thermal expansion between the connected materials for accurate mechanical characteristics and performance.

Design Considerations When Machining With Kovar Alloy: Using High Speed Steel Tools

When machining Kovar alloy, there are some vital factors to consider in design aspects because of the unique properties of Kovar. Working with high-performance nickel alloys like Kovar, Invar, and Inconel involves challenges and considerations such as control over heating, the use of specific cutting fluids like sulfurized mineral oil, and the importance of tooling and machining techniques to prevent warping and ensure precision. Kovar usually serves as a controlled expansion alloy for achieving high dimensional stability in precision instruments.

Thermal Expansion: While connecting Kovar materials with other materials, match the CTE (coefficient of thermal expansion) of Kovar and adjacent materials to avoid any mechanical and thermal stress and strain during operating temperatures.

Machining Speeds and Feeds: Kovar machining requires slower speeds and higher feeds to minimize the work hardening that occurs due to the material’s greater toughness and strength compared to conventional steels. Use approximately the same speed for different diameter holes and ensure the hole is cleaned properly to maintain optimal machining conditions.

Tooling: To optimize the machining of Kovar alloy, it is advisable to use carbide tools. The material is abrasive and will wear rapidly if soft tools such as high-speed steel are used. Cemented carbide (also known as tungsten carbide or hardmetal) is harder than Kovar, allowing you to achieve excellent tool life. Just make sure to handle carbide tools as directed, since they are brittle and prone to chipping if subjected to excessive forces or misused.

Annealing: Pre-anneal the Kovar part before machining to relieve the furnishing and work hardening and controlled post-annealing after machining, to keep dimensional and mechanical stability.

Surface Treatment: Apply a surface finishing treatment to eliminate the oxidation, plating contamination, and coating because it can extend the lifetime of the Kovar part and enhance solderbility.

Applying these design considerations to your Kovar CNC machining project can ensure suitable physical and mechanical performance for Kovar alloys.

Challenges and Solutions in Kovar Alloy Machining: How to Control Heat Buildup

1. Work Hardening: Kovar is susceptible to work hardening during machining, which can make the process difficult and degrade tool life.
   • Solution: To counteract this, it is advisable to half the drill speed and maintain low cutting speeds overall. Additionally, ensure thorough lubrication to reduce heat generation significantly, which helps in minimizing the risks of hardening. Using these strategies optimizes the machining process and prolongs the lifespan of your carbide tools.
2. Tool Wear: The toughness of Kovar and its abrasive nature can lead to increased wear and tear on cutting tools.
   • Solution: Use carbide or other hard-tipped cutting tools which can withstand the demands of machining Kovar and maintain sharpness longer.(Diamond-coated Tools, high speed steel tools)
3. Thermal Expansion Management: Kovar’s property of controlled thermal expansion can be problematic if not properly managed during the machining process.
   • Solution: Pre-plan the machining process to account for thermal expansion based on the part’s operating temperature environment.
4. Surface Oxidation: Kovar can develop an oxide layer when heated, which can affect the quality of the machined surface.
   • Solution: Control the machining environment and speed to minimize heating, and consider post-machining treatments such as passivation to enhance surface properties.
5. Internal Stress: Kovar parts can develop internal stresses if improper annealing procedures are followed.
   • Solution: Anneal the parts properly before machining to relieve stresses, and potentially after machining to stabilize the part.

Understanding these challenges and implementing the appropriate solutions can significantly improve the machining quality of Kovar alloy, ensuring that the final components meet precise dimensional and operational requirements.

How AT-Machining Masters Kovar Alloy Manufacturing

AT-Machining, a company specializing in Kovar alloy manufacturing, uses advanced precision engineering capabilities designed specifically for the processing challenges that come with using Kovar material. AT-Machining has CNC machining capacity with top-of-the-line CNC software that enables programming and simulation and high-performance machines with specialized tooling for Kovar material features work hardening and thermal expansion characteristics.

The AT-Machining process prioritizes tight tolerances and excellent surface finishes so that each part exceeds specifications. Their machining process also involves planning and controlling machining parameters to optimize Kovar alloy properties such as its controlled expansion rate, which is especially critical for electronic and aerospace applications.

Conclusion: Making the Right Choice for Your Machining Needs

In conclusion, Kovar alloy is a high-value, versatile material suitable for custom machining. Especially applications necessitating accurate and reliable thermal expansion control. From its properties to meticulous machining approaches, Kovar alloy machining comes with several features and advantages over other metals. From aerospace components to electronic packaging and critical assemblies, machining parts from Kovar alloy guarantees repeatability and precision, meeting strict industry specifications and performance requirements.