Thermal and Atmospheric Boundary Control in Reactive-Metal Welding

The welding of titanium and zirconium is both interesting and challenging. Both alloys have a strong affinity for oxygen, nitrogen, and hydrogen at elevated temperatures. Oxygen and nitrogen act as interstitial strengtheners in the alpha phase, increasing strength and hardness while reducing ductility; excessive absorption can lead to embrittlement. Zirconium behaves similarly and is particularly sensitive to hydrogen from moisture sources. Because of this reactivity, titanium must be protected from atmospheric exposure until the weld and adjacent heat-affected zone cool below approximately 800°F (427°C), while zirconium requires inert shielding until the surface temperature drops below approximately 600°F (315°C).

Author: Travis Field, Pipe welding specialist, Pipe Welding Institute