Mechanical Properties of Lanthanum Containing-Cast Alloy 718 Welds

—Study on Weldability of Cast Alloy 718 (Report 9)—

Abstract

The present work was undertaken to examine the mechanical properties of lanthanum containing-cast alloy 718 laser welds. The 0.3 mass% lanthanum-added specimen (03 LaWP) was welded by CO₂ laser welding in argon gas atmosphere. The commercial cast alloy 718 produced by the sand mold casting was used in as-received condition and at the heat treatment to produce plates with three different levels of grain size, and they were also welded for comparison. All post-welding heat treatments of the joints were carried out in a vacuum furnace. The mechanical properties of the welded joints were evaluated from tensile properties measured in the temperature range of 298 K to 1073 K. The tensile strength of lanthanum added-cast alloy 718 laser welds decreased with increasing the test temperature. The tensile strength of 03 LaWP specimen was equal to or greater than that of base metal at any test temperatures. Compared with the commercial cast alloy 718 welds, 03 LaWP specimen had good tensile properties at room and high temperatures. Detailed fractography confirmed that the failure occurred in the base metal in all cases. The cause of improved tensile properties of lanthanum containing-cast alloy 718 laser welds could be due to grain size strengthening-effects.