Weldability of the superalloys Haynes 188 and Hastelloy X by Nd:YAG

Abstract

Abstract. The requirements for welded aircraft parts have become increasingly severe, especially in terms of the reproducibility of the geometry and metallurgical grade of the weld bead. Laser welding is a viable method of assembly to meet these new demands, because of automation, to replace the manual TIG welding process. The purpose of this study is to determine the weldability of Hastelloy X and Haynes 188 alloys by the butt welding process with a Nd:YAG laser. To identify the influential parameters of the welding process (laser power, feed rate, focal diameter and flow of gas) while streamlining testing, an experimental design was established with the CORICO software using the graphic correlation method. The position of the focal point was fixed at 1/3 of the thickness of the sheet. The gas flow rate and the power of the beam have a major effect on the mechanical properties and geometry of the weld. The strength of the weld is comparable to that of the base metal. However, there is a significant decrease in the elongation at break of approximately 30%. The first observations of the cross section of the weld by scanning electron microscopy coupled with EBSD analysis show a molten zone presenting dendritic large grains compared to the equiaxed grains of the base metals without a heat affected zone.

Yb: YAG Laser Welding of Aeronautical Alloys

“…The laser beam can be carried by the core of the fiber; the focal diameter is considered small (SFC). It can also be carried by the periphery of the fiber, which then corresponds to the large focal configuration (LFC) [7][8]. To validate the weldability of these alloys, dimensions of weld section are measured and compared to standard specifications described in NF L06-395-2000.…”

Influence of Yb:YAG Laser Beam Parameters on Haynes 188 Weld Fusion Zone Microstructure and Mechanical Properties

“…[18] The CORICO method is based on an analysis of partial correlations between all the variables of the experimental design. [19] The CORICO software calculates correlations between factor and responses, and retains only significant correlations.…”

“…We considered as optimal welding parameters those which minimized the size of defects (low weld, drop-thru, underfill, undercut, and shrinkage groove) while maximizing the width of the weld, gas shield, and mechanical properties (ultimate tensile strain and elongation at rupture). [18] The corresponding optimal welding parameters are given in Table I.…”