Tungsten submerged arc welding using powdered flux

Abstract

A tungsten submerged arc welding process wherein a non-consumable electrode (18) provides an arc (16) under a protective bed of flux powder (26), thereby eliminating the need for an inert cover gas supply. The arc melts a feed material in the form of alloy powder (22) or filler wire (40) along with a surface of a substrate (12) to form a layer of cladding material (10, 32) covered by a layer of slag (20, 44). The flux and slag function to shape the deposit, to control cooling, to scavenge contaminants and to shield the deposit from reaction with air, thereby facilitating the deposit of previously unweldable superalloy materials.

Description

FIELD OF THE INVENTION[0001]This invention relates generally to the field of metals joining, and more particularly to the welding clad buildup and repair of superalloy materials.BACKGROUND OF THE INVENTION[0002]Welding processes vary considerably depending upon the type of material being welded. Some materials are more easily welded under a variety of conditions, while other materials require special processes in order to achieve a structurally sound joint without degrading the surrounding substrate material.[0003]Common arc welding generally utilizes a consumable electrode as the feed material. In order to provide protection from the atmosphere for the molten material in the weld pool, an inert cover gas or a flux material may be used when welding many alloys including, e.g. steels, stainless steels, and nickel based alloys. Inert and combined inert and active gas processes include gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding or wolframite inert g...

AI Technical Summary

Benefits of technology

The patent text discusses the difficulty of welding superalloy materials due to their susceptibility to weld solidification cracking and strain age cracking. The technical effect of this patent is to provide a method for weld repairing superalloy materials using a flux material and a chill plate to limit the heating of the substrate material and minimize the heat input of the process. This method can be used in various repair applications where the geometry of the parts does not facilitate the use of a chill plate. Additionally, the patent discusses the use of selective laser melting or selective laser sintering to melt a thin layer of alloy powder particles onto an alloy substrate, with the melt pool being shielded from the atmosphere by applying an inert gas.

Problems solved by technology

It is recognized that superalloy materials are among the most difficult materials to weld due to their susceptibility to weld solidification cracking and strain age cracking.

However, hot box welding is limited by the difficulty of maintaining a uniform component process surface temperature and the difficulty of maintaining complete inert gas shielding, as well as by physical difficulties imposed on the operator working in the proximity of a component at such extreme temperatures.

However, this technique is not practical for many repair applications where the geometry of the parts does not facilitate the use of a chill plate.

These processes tend to trap rather than eliminate or remove the oxides (e.g. aluminum and chromium oxides) that are adherent on the surface of the particles within the layer of deposited material, resulting in porosity, inclusions and other defects associated with the trapped oxides.

For some superalloy materials in the zone of non-weldability there is no known acceptable welding or repair process.

Furthermore, as new and higher alloy content superalloys continue to be developed, the challenge to develop commercially feasible joining processes for superalloy materials continues to grow.

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