Preparation of filler-metal weld rod by injection molding of powder

Abstract

A filler-metal weld rod of a filler-metal composition is prepared by providing a mass of metallic powders, mixing the metallic powders with a temporary thermoplastic binder to form an injection-moldable mixture, and thereafter injection molding the injection-moldable mixture at an injection-molding temperature above the thermoplastic temperature of the thermoplastic binder to form an injection-molded rod. Any excess thermoplastic binder is removed from the injection-molded rod, and the injection-molded rod is thereafter sintered to form a filler-metal weld rod, with the temporary thermoplastic binder removed in the step of sintering.

Description

[0001] This invention relates to the preparation of filler-metal weld rod and, more particularly, to the preparation of weld rod of difficult-to-deform alloys. SUMMARY OF THE INVENTION [0002] In a form of welding, a metallic article to be welded is locally melted, and the melted metal is mixed with a second metal. The temperature is thereafter reduced so that the melted mixture solidifies. In one approach, the second metal is another article, so that the two articles are joined together. In another approach, the second metal is an overlay deposit that is also melted during the welding process, with the result that the first article is overlaid with the second metal. [0003] A filler metal may be used in either of these approaches. In the joining of two articles by welding, the filler metal may be added into the melted zone to fill the space between the two articles. In the overlay process, the filler metal may form substantially the entire overlay. The filler metal may be the same as...

AI Technical Summary

Benefits of technology

[0008] The present approach provides a method for producing filler-metal weld rod that is widely applicable. However, the process is most advantageously applied to weld rod wherein the filler metal is a difficult-to-work material such as a high-gamma prime nickel-base superalloy or a titanium aluminide, because there is no gross deformation of the weld rod required during the manufacturing process. The present approach produces a weight yield of usable weld rod, as compared with the weight of the starting material, of near 100 percent. There is excellent process economics and reduced cost of the weld rod. The quality of the weld rod is high, with low incidence of defects that can be transferred to the welded structure. New compositions may be readily prepared by the present approach.

[0015] The present approach provides a convenient and economical approach to producing filler-metal weld rod. Filler-metal weld rod of any composition that is available in powder form may be made, even of difficult-to-draw metals such as high-gamma prime nickel-base superalloys and intermetallics. Compositional control of the weld rod is highly precise. New compositions may be readily produced, without the extensive experimentation and process development required in most other processes when making weld rod of a new composition. The oxygen content of the final weld rod is below that expected from the oxygen contents of the starting materials, suggesting a chemical reaction and removal of the oxygen.

Problems solved by technology

Otherwise, some alloying is required during the processing or the use of the weld rod in a welding procedure, and there is a possibility of incomplete alloying although full alloying occurs during the subsequent welding operation.

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