One of the key differentiators between friction welding and other welding techniques is the ability to join dissimilar metals or two different materials that may be impossible to join by other techniques. Doing so is a cost-effective way to get the benefits of both materials.
How the Friction Welding Process Joins Dissimilar Metals
In conventional fusion welding, liquefied metals can react at the joint and form brittle intermetallic compounds. As these compounds solidify, they may weaken the weld, reduce toughness, and compromise long-term performance.
Friction welding uses a proven solid-state welding process to weld dissimilar metals without melting the base materials. Instead, it joins the two components in a plasticized condition under carefully controlled welding parameters. The result is a high-strength joint that can perform as well as—or even stronger than—the parent metal.
This advanced bimetallic welding method also creates a refined microstructure at the weld interface, supporting strong mechanical and metallurgical properties, reduced brittleness, and dependable performance across demanding applications.
Key Weld Zones in Bi-Metallic Friction Welding
- Base Material – The area of the parent materials unaffected by the friction welding cycle, retaining its original properties.
- Heat-Affected Zone (HAZ) – This region experiences thermal exposure without plastic deformation. Friction welds have narrow HAZs, helping preserve strength, minimize distortion, and improve corrosion resistance.
- Thermo-Mechanically Affected Zone (TMAZ) – This zone undergoes elevated temperature and deformation, producing elongated grains. It experiences partial structural change, but not full recrystallization.
- Center Weld Zone – At the center of the weld, intense heat and pressure during the joining cycle create dynamic recrystallization. This fine-grain structure often enhances hardness and improves overall weld performance relative to the parent metals.
Possible Combinations for Friction Welding Dissimilar Metal Materials
Typically, we can use any of the friction welding technologies to weld dissimilar metals, and the following are some common bi-metallic combinations and applications:
- Copper & Aluminum – Using linear friction welding, we can join copper to aluminum to form a heat plate. We want the heat-transfer properties of copper, but copper doesn’t bond to other surfaces very well or with sufficient rigidity, so we weld it to the aluminum, which then serves as the mounting surface.
- Copper & Copper – For electrical conductivity, we can use two different types of copper. A softer copper alloy that is much less expensive can be mounted to a harder copper alloy using rotary friction welding. Since the harder alloy is more expensive, you can selectively put it only in the spots where it is needed, where there will be wear characteristics on the finished part.
- Carbon Steel & Stainless Steel – A submersible pump motor with a bi-metallic motor shaft requires the magnetic properties of carbon steel and the corrosion resistance of stainless steel.
- Heat-Resistant Steel & Wear-Resistant Steel – Engine valves, such as high-stressed exhaust valves, utilize rotary friction welding to bond heat-resistant steel for the valve head with the abrasive wear-resistant steel for the valve stem.
- Aluminum & Inconel – For rocket transition points, it is absolutely critical to have a leak-proof joint between two different materials. Instead of using a mechanical joint, friction welding offers a simpler and more dependable alternative.
- Gear Steel & Standard Steel – In certain applications, it is necessary to mount a gear on a cylindrical steel base. For parts like this, manufacturing them as an assembly is not cost-effective. It is much easier to cut the gear teeth before welding and then weld the two materials together.
These examples show how beneficial the ability to friction-weld bi-metallic parts can be. We have the flexibility of choosing a specific metal to take advantage of its unique properties, ranging from electrical conductivity and heat resistance, to corrosive resistance, and combine it with another metal with its own beneficial properties. Also, bi-metallic parts allow us to use expensive materials only where needed. This advantage allows us to make cost-effective, high-performance parts.
MTI Can Solve Your Problems
As you can see, MTI offers the unique ability to truly customize parts to serve your applications best, while reducing costs. Talk with our expert engineers today to identify your needs and let us design a specialized solution for you. We’ll build a machine that makes your part, we’ll make the part for you, or we’ll help you make the part even better.
To learn more about friction welding, view our process or watch how friction welding can be put to work for you.