MASS-TRANSPORT DURING LASER-WELDING OF STAINLESS-STEELS AND ALLOYS USED BY UNITED-STATES-NAVY

Lasers, though developed only about a quarter century ago, are now being routinely used in the automotive, aerospace and other industries to produce superior quality, high-speed autogenous welds with narrow heat-affected zones in a number of alloys. However, they cannot at present be used to successfully weld certain important structural alloys due to a change in weld composition resulting from selective mass transport of certain alloying elements from the laser-melted region. The loss of alloying elements leads to a degradation in mechanical properties of laser-welded structures. Extensive experimental and theoretical research has previously been conducted to develop a better understanding and control of mass transport that takes place during high-energy laser welding. In light of the possible use of high-energy lasers for deep penetration welding of certain hard-to-weld structural alloys used in Navy vessels, the approach and results of these mass-transport studies has been applied to evaluate the suitability of lasers for welding alloys used by the US Navy. Details of the study are discussed.