Patent Application
20160175991
The disclosure relates generally to weld filler metals for superalloys.
Superalloys, especially those which are nickel based with a high y′ volume percent, for instance, greater than 30%, typically have a poor weldability. As a result, fusion welding of such superalloys often results in liquation and strain age cracking of the superalloy.
Gas turbine components made of superalloys are typically cast using investment casting process. Defects such as porosity and inclusions are typically found in the castings. The castings can either be scrapped or the defects can be repaired using joining methods. Scrapping of parts result in overall increase in the price of the castings. Hence it is imperative to salvage these castings. Typically such defects are repaired by fusion welding using gas tungsten arc welding (GTAW) process. Lower strength filler metals are typically used to minimize cracking in the weld and base metal heat affected zone (HAZ).
Embodiments of the invention disclosed herein may include a weld filler metal for a superalloy for welding, the weld filler metal comprising: a preformed article including: a first material with a melting point of approximately 2300 to 2500° F.; and a second material with a melting point of approximately 1800 to 2200° F., wherein a ratio of the first material and the second material is variable.
Embodiments of the invention may also include a method of welding a superalloy, the method comprising: applying a preformed article to an area of the superalloy, the preformed article including: a first material with a melting point of approximately 2300 to 2500° F.; and a second material with a melting point of approximately 1800 to 2200° F., wherein a ratio of the first material and the second material is variable; and welding the preformed article and the superalloy.
These and other features of the disclosure will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various aspects of the invention.
It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings. The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
As described herein, superalloys, especially nickel based alloys, have a very poor weldability. Attempts to fusion weld defects of these superalloys often result in cracking and other defects. In some embodiments, the superalloys can comprise alloys such as IN738, Rene80, IN939, GTD111, GTD444, and R108. Articles made from these superalloys have demonstrated porosity and inclusions when cast. Weld filler metals according to embodiments of this disclosure allow for welding of the defects, reducing scrap of cast superalloy articles.
A preformed article 110 of the disclosed weld filler material may be used to weld into an area 120 of superalloy 100. Preformed article 110 can include a first material, the first material having a high melting point. The high melting point can include, in some embodiments, a melting point in a range of approximately 2300° F. to 2500° F., plus or minus 50° F. The first material can be chosen from a group including, for instance, MM247, IN738, R80, IN939, R142, and R195. In embodiments where the superalloy is cobalt based, the first material may be chosen from H188, H25, and FSX414. These materials are further outlined in Table 1 below. The values are given as weight percent, and the nominal values should be understood to include ranges of weight percentage.
Preformed article 110 can also include a second material, the second material having a low melting point. The low melting point can include, in some embodiments, a melting point in a range of approximately 1800° F. to 2200° F., plus or minus 50° F. The second material can be chosen from a group including, for instance, DF4B, BRB, DF6A, D15, AMS4777, and BNi-9. In embodiments where the superalloy is cobalt based, the second material may be chosen from BCo-1 and MarM509B. These materials are further outlined in Table 1 below. The values are given as weight percent, and the nominal values should be understood to include ranges of weight percentage.
Properties of the preformed article can be controlled in multiple ways. For instance, by choosing a material chemistry of the first material and a material chemistry of the second material, the exact material chemistry and melting point of preformed article 110 can be controlled. By combining the first material and the second material, a ratio of the two materials can remain variable. For instance, the ratio of the two materials can be determined based on a material content of superalloy 100 to which preformed article 110 will be applied and welded, a melting point of superalloy 100, or both. That is, the material property of the filler weld metal of preformed article 110 can be optimized for superalloy 100 by choosing a ratio of the first material and the second material in order to alter the melting point. A combination of high melting point and low melting point materials allows for a broad range of properties of preformed article 110.
In some embodiments, preformed article 110 may include a cobalt based system, a nickel based system, or some combination thereof. That is, the material chemistry of weld filler metal of preformed article 110 may include substantially nickel, substantially cobalt, or a combination of both. For instance, in some embodiments, preformed article 110 may include H188, H25, FSX414, or MarM509B. In some embodiments, preformed article 110 may comprise a wire shaped article. However, in other embodiments, preformed article 110, as shown in
In contrast, embodiments of the present disclosure utilize welding techniques. That is, preformed article 110 (
As such, embodiments of the disclosure include welding preformed article 110 to superalloy 100 (
By using methods of embodiments of the disclosure, unlike previous welding techniques, the weld will not crack, and unlike brazing, superalloy 100 avoids high heating of the whole part. Further, preformed article 110 application according to embodiments of the present disclosure results in a denser deposit of material than brazing according to previous attempts.
According to some embodiments, a further advantage of methods of the disclosure are that once preformed article 110 has been applied to and welded to superalloy 100, additional materials can be welded to the combination. Due to the chemistry of preformed article 110, a second material, which can comprise traditional filler metals, can be added to a second layer to be welded in S4 (
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
