What method is used to join different alloys of valve stem and head in a cylinder valve?

The method used to join different alloys of valve stem and head in a cylinder valve is referred to as inertial welding. This technique involves the use of mechanical energy to create high temperatures at the interface of the materials being joined. Inertial welding is particularly advantageous for this application as it allows for a solid-state bond without melting the materials, which preserves their physical properties.

Inertial welding is particularly effective for joining different alloys because it minimizes the risk of issues like phase changes, which can occur if traditional welding methods are employed. These issues can affect the integrity and durability of the valve components. The process is also relatively quick and does not require filler materials, which can be important for maintaining the desired characteristics of the valve components.

This method is well-suited for high-performance applications such as engine valves, where the strength and reliability of the joint are critical for performance. In contrast, methods like hard-surfacing, adhesive joining, or using threads may not provide the same level of mechanical integrity or could introduce material incompatibilities, making them less preferable for this specific application.