Patent Publication Number: US-2022234101-A1

Title: Crack healing additive manufacturing of a superalloy component

Description:
TECHNICAL FIELD 
     The present disclosure is directed, in general, to a system and method for repairing and manufacturing high-temperature superalloy components, and more specifically to such a system and method for the repair and manufacturing of gas turbine blades and vanes. 
     BACKGROUND 
     The difficulties associated with the additive manufacture (AM) of nickel-base gas turbine components with high gamma-prime (γ′) content makes the process unsuitable for large scale manufacturing or repair. In particular, attempts to additively manufacture components using a CM 247 LC branded superalloy, or to repair such components often result in grain boundary melting and cracking. Alternatively, the components are repaired with another inferior nickel base alloy that is less prone to cracking, resulting in poor performance of the component. 
     SUMMARY 
     Variously disclosed embodiments include systems and methods that may be used to facilitate additively manufacturing components (or portions thereof) made from one or more superalloys. In an aspect, a method of additively manufacturing includes successively depositing and fusing together layers of a superalloy powder mixture comprised of a base material powder and a eutectic powder, to build up an additive portion. The eutectic powder has a solidus temperature lower than the solidus temperature of the base material powder. In addition, the method includes heat treating the additive portion at a temperature greater than 1200° C. to heal cracks and/or fill pores and to homogenize the alloy of which the additive portion is comprised. The additive portion alloy has a chemistry defined by the superalloy powder mixture. Also, the base material powder is formed of a nickel-base superalloy with an aluminum content by weight of at least 1.5%. 
     In a further aspect, the method may in include removing a damaged portion from a component to leave a first interface; printing a replacement portion via successively the depositing and fusing together layers of the superalloy powder mixture, which replacement portion has a second interface surface; and attaching the second interface surface to the first interface surface to replace the damaged portion of the component. 
     Further aspects may include the superalloy powder mixture comprised of at least 76% by weight of the base material alloy and at least 6% by weight of the eutectic powder. 
     In aspects, the eutectic powder may be a nickel-base alloy including by weight about 6% to about 11% chromium, about 5% to about 9% titanium, and about 9% to about 13% zirconium, with balance nickel and optional incidental elements and unavoidable impurities. 
     The foregoing has outlined rather broadly the technical features of the present disclosure so that those skilled in the art may better understand the detailed description that follows. Additional features and advantages of the disclosure will be described hereinafter that form the subject of the claims. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiments disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure in its broadest form. 
     Also, before undertaking the Detailed Description below, it should be understood that various definitions for certain words and phrases are provided throughout this specification and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases. While some terms may include a wide variety of embodiments, the appended claims may expressly limit these terms to specific embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal section view of a gas turbine engine. 
         FIG. 2  is a perspective view of several vanes of the gas turbine engine of  FIG. 1 . 
         FIG. 3  is a perspective view an insert piece for use in repairing a turbine vane of  FIG. 2 . 
         FIG. 4  is a perspective view of the vanes of  FIG. 2  with the insert piece of  FIG. 3  being installed. 
         FIG. 5  is a perspective view of a component 3D printed to a near net shape. 
         FIG. 6  is a perspective view of the component skeleton after removal of a binder and sintering. 
         FIG. 7  is a perspective view of the component skeleton during an infiltration of a melting point depressant. 
         FIG. 8  is a perspective view of the completed near net shape component following infiltration. 
         FIG. 9  is a perspective view of another component 3D printed to a near net shape. 
         FIG. 10  is a perspective view of the component skeleton of  FIG. 9  after removal of a binder and sintering. 
         FIG. 11  is a perspective view of the component skeleton of  FIG. 9  during an infiltration of a melting point depressant. 
         FIG. 12  is a perspective view of the completed near net shape component following infiltration and during removal of a gate. 
         FIG. 13  is a perspective view of an attachment PSP for use in a leading-edge repair process. 
         FIG. 14  is a perspective view of a leading-edge replacement component attached to the attachment PSP of  FIG. 13 . 
         FIG. 15  is a perspective view of a portion of a gas turbine blade having operating damage in the form of tip corrosion and tip cracking. 
         FIG. 16  is a perspective view of the blade of  FIG. 15  with the damaged portion of the blade removed. 
         FIG. 17  is a perspective view of a replacement tip for the repair of the damaged blade of  FIG. 16 . 
         FIG. 18  is a perspective view of an attachment PSP for use in repairing the blade tip of  FIG. 16 . 
         FIG. 19  is a perspective view of the damaged blade of  FIG. 16 , the attachment PSP of  FIG. 18 , and the replacement tip of  FIG. 17 . 
         FIG. 20  is a perspective view of replacement tip in a “green-form” during the manufacturing process. 
         FIG. 21  is a perspective view of the replacement tip of  FIG. 20  after sintering and removal from the manufacturing support member. 
         FIG. 22  is a perspective view of the replacement tip of  FIG. 21  installed onto the blade of  FIG. 16 . 
         FIG. 23  is a perspective view of a gas turbine vane with a damaged portion removed. 
         FIG. 24  is a perspective view of a pre-sintered preform (PSP) replacement piece and a PSP attachment piece sized to repair the damaged portion of  FIG. 23 . 
         FIG. 25  is a perspective view of the pre-sintered preform (PSP) replacement piece of  FIG. 24 . 
         FIG. 26  is a flowchart illustrating one process for forming a PSP. 
         FIG. 27  is a flowchart illustrating an alternative process for forming a PSP. 
         FIG. 28  is an image of a cross-section of a sample block additively manufactured via an example crack healing superalloy powder mixture. 
         FIG. 29  is an image of a cross-section of a sample block additively manufactured from a single CM 247 LC superalloy powder. 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
     Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments. 
     Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including,” “having,” and “comprising,” as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and/or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, etc. described with regard to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary. 
     Also, although the terms “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure. 
     In addition, the term “adjacent to” may mean: that an element is relatively near to but not in contact with a further element; or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard as available a variation of 20 percent would fall within the meaning of these terms unless otherwise stated. 
       FIG. 1  illustrates a gas turbine or combustion turbine engine  10  that includes a compressor section  15 , a combustion section  20 , and a turbine section  25 . During operation, atmospheric air is drawn into the compressor section  15  and compressed. A portion of the compressed air is mixed with a fuel and combusted in the combustion section  20  to produce high-temperature products of combustion. The products of combustion are mixed with the remaining compressed air to form exhaust gas that then passes through the turbine section  25 . The exhaust gas expands within the turbine section  25  to produce torque that powers the compressor section  20  and any auxiliary equipment attached to the engine  10 , such as an electrical generator. The exhaust gas enters the turbine section  25  at a high temperature (1000 degrees F., 538 degrees C. or greater), such that the turbine blades  30  and vanes are exposed to high temperatures and must be manufactured from materials suited to those temperatures. The terms “blade” and “vane” should be read as being interchangeable. While typically, the term “blade” refers to rotating air foils and “vane” refers to stationary airfoils, the invention should not be limited to these definitions as most repairs or processes are equally applicable to both blades and vanes. 
     In one construction, the vanes  30  are manufactured from a nickel-base superalloy such as CM 247 LC superalloy.  FIG. 2  illustrates a portion of the stationary vanes  30  from the turbine section  25  of the engine  10  of  FIG. 1 . Each vane  30  includes a leading edge  35 , a trailing edge  40 , a suction side  45 , and a pressure side  50 . Adjacent vanes  30  cooperate with one another to define a flow path therebetween. The exhaust gas passes through the flow paths and is directed and accelerated as desired to provide an efficient expansion of the exhaust gas and to provide torque to a rotor  53  that in turn drives the auxiliary equipment. 
     During operation, the vanes  30  can become damaged. Damage can be caused by foreign object impacts, high temperature operation, fatigue, creep, oxidation, and the like. One area that is susceptible to damage is the leading edge  35  of the vane  30 .  FIG. 2  illustrates one of the vanes  30  with a portion  55  of the leading edge  35  removed. A desired repair would include replacing the removed portion  55  with a material that closely matches the base material. However, nickel-base superalloys such as those used to manufacture the vanes  30  are not conducive to welding or typical additive manufacturing repair processes. 
       FIGS. 3 and 4  illustrate one possible repair for the leading edge  35  of the vane  30  illustrated in  FIG. 2 .  FIG. 3  illustrates an insert piece in the form of a leading edge insert  60  and  FIG. 4  illustrates the positioning of the leading edge insert  60  in the vane  30  for attachment. The insert  60  includes a substantial portion of matching base material and is typically attached using a brazing process. 
       FIGS. 5-12  illustrate a process for manufacturing the insert piece  60  illustrated in  FIG. 3  or any other repair component desired.  FIGS. 5-8  illustrate the process for a generic cube-shaped object  65  while  FIGS. 9-12  illustrate a similar process for the leading edge insert  60  illustrated in  FIG. 3 . 
     The process begins by mixing a high γ′ forming nickel-base powder  66  (base material) with a binder  67  and 3D printing or otherwise additively manufacturing a green form of the desired component  70 ,  75  to a near net shape. The green form component  70 ,  75  is then allowed to dry.  FIGS. 5 and 9  illustrate this step. During the printing or additive manufacturing process, the base material is not melted. As used herein, the term “near net shape” means that the component falls within the desired manufacturing parameters and tolerances for the component at a particular step in the manufacturing process without further machining. However, some surface grinding or polishing may be required to achieve a desired surface finish or texture for the final component. In addition, additional layers or coatings may be applied to the component to complete the component for use. Furthermore, and as illustrated in  FIGS. 9-12  the green form component  75  may include features such as gates  80 , or support structures that are used during the manufacturing process and then removed. The green form component  75 , including features such as these would be considered near net shape as additional machining or processing is not required before the additional manufacturing steps are performed and all that is required is the removal of the unwanted features (gate  80 ). 
     The next step is the placement of the green form component  70 ,  75  into a furnace or other heating device. The green form component  70 ,  75  is heated to burn or remove the binder  67 . The remaining material defines a skeleton  85 ,  90  made up of the base material  66  and gaps or empty areas  68  formerly occupied by the binder material  67 . In  FIG. 6 , the skeleton  85  is a cube-shape. In  FIG. 10  the skeleton  90  defines an intermediate component that will ultimately become the leading edge insert  60  and further includes the gate  80 . In preferred arrangements, the heating or sintering step does not melt the base material  66  and leaves at least eighty percent of the volume of the skeleton  85 ,  90  as base material  66 , thereby leaving no more than twenty percent of the skeleton  85 ,  90  as empty space  68 . This is referred to herein as twenty percent porosity or less. The amount of binder  67  used, and the sintering temperature are selected to arrive at less than twenty percent porosity and preferably between five percent and twenty percent porosity. 
     As illustrated in  FIGS. 7 and 11 , the skeleton  85 ,  90  and the gate  80  are infiltrated with low melting point material, or melting point depressant  100  (sometimes referred to as braze material). Preferred compositions of the melting point depressant  100  include at least one of titanium (Ti), zirconium (Zr), and hafnium (Hf) with the balance being chromium (Cr) and nickel (Ni). The use of boron (B), silicon (Si), or phosphorous (P) in part or in whole as the melting point depressant  100  is avoided to prevent the negative effects these materials have on the material properties of the completed component  60 ,  65 . 
     To produce the desired infiltration, the melting point depressant  100  is melted in a manner that assures that the liquid melting point depressant  100  is in contact with the skeleton  85 ,  90 . Capillary action produced by the porosity in the skeleton  85 ,  90  pulls the liquid melting point depressant  100  into the pores  68  of the skeleton  85 ,  90  and can result in a completed component  60 ,  65  that is ninety-nine percent filled with material (i.e., one percent porosity). 
     The specific composition of the melting point depressant  100  is selected based at least in part on the quantity of titanium included in the base material. For example, in constructions that include 3.5 percent or more titanium by weight in the base material, the desired melting point depressant  100  includes at least one of Hf and Zr with the remainder being Ni and Cr. In constructions with 1.0 percent or less Ti in the base material, the preferred composition includes Ti with the balance being Ni and Cr. When the quantity of Ti is between 1.0 percent and 3.5 percent in the base material, the desired composition includes at least one of Zr, and Ti with the balance being Ni and Cr. The quantity of Ti, Zr, or Hf are selected such that the completed nickel-base component has less than 6.0 percent Ti (with other constructions being below 5.0 percent and still others below 4.0 percent). 
     Once the infiltration is complete, any features added for manufacturing requirements such as the gate  80  or a support structure illustrated in  FIGS. 9-12  are removed to complete the component  60 ,  65 . Any additional grinding, polishing, or layer additions can now be performed prior to the installation of the component  60 ,  65  as illustrated in  FIG. 4 . In preferred constructions, following infiltration, the component  60 ,  65  has less than one percent porosity. 
     The process described herein does not melt the base material powder  66 . Rather, the powder  66  is mixed with the binder  67 , 3D printed using a laser source or other energy source and dried. The binder  67  is burned out at low temperature (e.g., &lt;500 C.). The remaining base material  66  is heated up to a sintering temperature that assures a maximum of twenty percent porosity is left in the sintered material. 
     For nickel-base alloys, the amount of titanium employed is preferably limited to around six percent (i.e., between four and eight percent) to reduce the likelihood of reduced mechanical properties. Due to this limitation, the level of porosity in the skeleton  85 ,  90  is determined, at least in part by the amount of titanium in the base material and in the braze material  100  (sometimes referred to as melting point depressant) with the goal being about six percent titanium in the finished component  60 ,  65 . For example, in one construction, the base material or the skeleton  85 ,  90  may include no titanium. If a braze material that contains 22% titanium is employed, the total porosity of the skeleton  85 ,  90  would be limited to about 30% which leads to a completed component  60 ,  65  with about 6.6% titanium. 
     In another example, the skeleton  85 ,  90  includes 1% titanium. In this case, using the same braze material with 22% titanium, the skeleton  85 ,  90  should be limited to less than 20% porosity to arrive at a finished component  60 ,  65  having about 5.2% titanium. 
     In yet another example, the skeleton  85 ,  90  includes 2% titanium. In this case, using the same braze material with 22% titanium the skeleton  85 ,  90  should be limited to less than 15% porosity to arrive at a finished component  60 ,  65  having about 6.0% titanium. 
     As discussed, nickel-base gas turbine components, specifically CM 247 LC superalloy components, are difficult to repair or build-up with any method that involves melting of the component since the grain boundary melting (incipient melting) temperature is low with respect to the welding temperature such that the weld repair often generates cracks during the repair process. 
     As discussed with regard to  FIGS. 2-12 , one alternative to weld repair is to first build a replacement component  60 ,  65  (a pre-sintered preform (PSP)) for the damaged section of the vane  30  and then join this new replacement component  60 ,  65  to the component being repaired (e.g., vane  30 ) using a process that assures a maximum temperature that remains below the grain boundary melting temperature. To further improve this repair, one could replace the damaged section of the component being repaired with a replacement component  60 ,  65  that includes a functional material that provides a higher oxidation resistance than the base material of the component being repaired (e.g., vane  30 ). 
     The damaged portion  55  is removed and replaced with a close-fitting replacement component  105  made using additively manufactured (AM) material or a pre-sintered preform (PSP) that provides similar or better oxidation and rupture properties. When the replacement component  105  is a replacement for the leading edge  35  as illustrated in  FIGS. 2-4 and 9-12 , additively manufactured replacement components  105  can include columnar grains with significant rupture capability. 
     To perform a repair of the leading edge  35  with a high oxidation resistant material, the damaged portion  55  of the leading edge  35  of the vane  30  is first removed. The removed damaged portion  55  is measured to determine the size and configuration of the replacement component  105  that will be installed. The replacement component  105  is then manufactured using an additive manufacturing process or as a PSP, such as a PSP made using a process as described with regard to  FIGS. 2-12 . To enhance the oxidation resistance of the replacement component  105 , the material used to manufacture it, when using an additive manufacturing process includes up to eight percent (8%) aluminum. In addition, attachment structures  110  such as pins, protrusions, notches, apertures, etc. can be formed as part of the replacement component  105  to enhance or create an interlock between the replacement component  105  and the vane  30  or other component being repaired. 
     When the replacement component  105  is manufactured as a PSP the preferred material includes up to eighty percent (80%) superalloy (preferably matching the vane  30  being repaired), up to eight percent (8%) aluminum, and up to thirty percent (30%) braze material including Ti, Zr, and Hf as described above. As with the additively manufactured replacement component  105 , the PSP replacement components  105  can include attachment structures  110  like those described above.  FIGS. 9 and 10  illustrate attachment structures  110  in the form of alignment pins  111 . The pins  111  align with and engage apertures formed in the blade  30  to which the replacement component  105  will attach. While the pins  111  are illustrated in only  FIGS. 9 and 10  for clarity, in preferred constructions the pins  111  would be formed as part of the replacement component  105  and would therefore be present at each step of the manufacturing process. In other constructions, the pins  111  are separate components that are attached to the replacement component  105  at some point during its manufacture. Attachment could be facilitated using any suitable attachment means including but not limited to adhesives, welding, brazing, etc. 
     The material used to manufacture the PSP replacement component  105  is maintained at a temperature at least  50  degrees C. above the braze melting temperature for more than one hour to react a majority of the braze material with the base material powder. This prevents re-melting during the braze operation that attaches the replacement component  105  to the vane  30 . 
     An attachment PSP  115 , shown in  FIG. 13  is formed from a material combination similar to that described above with regard to the PSP replacement component  105  with the exception that it includes at least thirty percent (30%) braze material rather than up to thirty percent (30%) braze material. The attachment PSP  115  is preferably no more than 250 microns thick and is produced at a similar temperature as the PSP replacement component  105  described above but is held at that temperature for a shorter time (less than 15 minutes). The attachment PSP  115 , therefore has enough unreacted braze material to be able to join the replacement component  105  as illustrated in  FIG. 14 , regardless of how it is manufactured (PSP or additive manufacturing) to the vane  30  being repaired. 
     The replacement component  105  has sufficient mechanical properties and oxidation resistance due to the adjusted composition and the Ni—Cr—(Ti, Zr, Hf) braze composition. In addition, when using the additively manufactured replacement component  105 , the columnar grains provide significant rupture capability over the base material of equiaxed grain structure. 
     It should be noted that the replacement component  105  can be manufactured in a number of different shapes and sizes and should therefore not be limited to the arrangement illustrated in  FIGS. 2-4 and 9-14 . For example,  FIGS. 23-25  illustrate a leading-edge repair that utilizes a replacement piece  250  (shown in  FIGS. 24 and 25  and sometimes referred to as a replacement piece) that includes a curved interface surface  255  as compared to the more rectangular or linear interface surface of  FIGS. 2-4 . 
     Specifically, and with reference to  FIG. 23 , a leading-edge  260  of a stationary vane  265  is illustrated with a portion removed. The removed portion  270  likely included damage such as cracks, spallation, impact damage, and the like that rendered it unsuitable for use. The damaged material, along with undamaged material is removed to define a vane interface  275  that is curved. The vane interface  275  could follow an elliptical or circular arc (when viewed in the circumferential direction) or any other curve desired. It is preferred that a continuous curve (when viewed in the circumferential direction), in the mathematical sense be employed but non-continuous curves or surfaces could be employed as well. The stationary vane  265  of  FIG. 23  includes a pressure side surface and a suction side surface spaced from the pressure side surface to define a hollow space. In this arrangement, a first interface surface is formed on the pressure side surface and a second interface surface is formed on the suction side surface. In preferred constructions, each of the first interface surface and the second interface surface follows the same continuous curve (when viewed in the circumferential direction). However, some constructions may employ different curves. In addition, as will be understood, the interface surfaces follow a complex three-dimensional path. However, when that path is projected onto a plane in the circumferential direction, that curve is preferably a continuous curve. 
     With the damaged portion removed, the replacement piece  250  can be manufactured. The replacement piece  250  could be manufactured using any of the various processes described herein and is manufactured to include the replacement surface  255  that is curved to closely match the vane surface  275  formed in the vane  265  through the removal of the damaged portion  270 . In addition, any cooling holes  285  or other internal features (e.g., ribs, etc.) are typically preformed in the replacement piece  250  before it is attached to the vane  265 . 
     The replacement surface  255  illustrated in  FIG. 25  includes a third interface surface and a fourth interface surface that are each curved to match the curves of the first interface surface and the second interface surface. Specifically, in preferred constructions, the third interface surface and the fourth interface surface define a continuous curve when projected in the circumferential direction onto a two-dimensional plane. Of course, the actual shape of the curve or curves is selected to match the first interface surface and the second interface surface. 
     As illustrated in  FIG. 24 , a PSP interface component  290  may also be manufactured to closely match the shape of the replacement surface  255  and the vane interface surface  275 . PSP interface components  290  are used to enhance the attachment of the replacement piece  250  to the vane  265  when material considerations or other considerations make it necessary. Of course, in some constructions, the PSP interface component  290  is not needed. 
     The replacement piece  250 , and the PSP interface component  290 , if needed are positioned as illustrated in  FIG. 24  such that they closely fit one another. A braze process is then performed using any of the braze materials discussed herein or any other braze material suitable for use with the particular materials of the vane  265  and the replacement piece  250  and the process in which the vane  265  ultimately operates. Once the braze is complete, the repaired vane  265 , or other component can be finished with any processes that might be necessary for the particular component (e.g., machining, grinding, polishing, coating application, etc.). 
     As will be described below, these processes and procedures can be applied to other components such as a tip  120  of the vane  30  or blade or some other component. 
     For example,  FIGS. 15-19  illustrate a process similar to that just described but for the repair of the tip  120  of a nickel-base gas turbine vane  30  or blade, and specifically a vane  30  or blade made from CM 247 LC superalloy or a similar material. 
       FIG. 15  schematically illustrates the blade  30  with tip section cracks  125  that extend downward in the blade  30 . The blade tip  120  also includes oxidation damaged portions  130  that can be common following operation of the turbine blade  30 . In order to repair the blade  30 , the damaged portion of the tip  120  is first removed. In the example of  FIG. 15 , the removal of the damaged portion  135  does not completely remove the cracks  125  but does remove the oxidation damaged portions  130 . It is desirable to minimize the amount of the tip  120  being removed such that in some circumstances, portions of the crack or cracks  125  may remain after removal. With reference to  FIG. 16 , any cracks  125  that remain after the removal of the damaged portion  135  are removed using a machining process, grinding, or other suitable material removal processes. 
     A closely fitting replacement tip  140  is formed to fill the space created by the removal of the damaged portion  135 . The replacement tip  140  may also fill any spaces created during the removal of any cracks  125 . Alternatively, the space opened during the removal of the cracks  125  can be filled with a powdered braze material during the attachment process for the replacement tip  140 . The replacement tip  140  can be formed using an additive manufacturing (AM) process or can be formed from a pre-sintered preform (PSP) that provides similar or better oxidation and rupture properties than the removed portion  135 . 
     The replacement tip  140 , when manufactured using an AM process is preferably composed of a material similar to the base material of the blade  30  with the addition of up to eight percent (8%) aluminum to provide superior oxidation resistance. In addition, attachment structures  110  such as pins  145 , illustrated in  FIG. 17 , can be used to enhance the mechanical connection between the replacement tip  140  and the remainder of the blade  30  being repaired. Of course, other features such as protrusions, apertures, bosses, etc. can be used as attachment structures  110 . The pins  145  of  FIG. 17  are received in corresponding apertures formed or otherwise existing in the remaining portion of the blade  30  being repaired. 
     In constructions in which a PSP is used in place of an AM replacement tip  140 , the material is preferably made of up to eighty percent (80%) superalloy (matching the base material of the blade  30  being repaired), up to eight percent (8%) aluminum, and up to thirty percent (30%) braze material including Ti, Zr, and Hf as described above. 
     The material used to manufacture the PSP replacement tip  140  is maintained at a temperature at least 50 degrees C. above the melting temperature of the braze material for more than one hour to react a majority of the braze material with the base material powder. This prevents re-melting during the braze operation that attaches the replacement tip  140  to the blade  30  being repaired. 
     A tip attachment PSP  150 , shown in  FIG. 18  is formed from a material combination similar to that described above with regard to the PSP replacement tip  140  with the exception that it includes at least thirty percent (30%) braze material rather than up to thirty percent (30%) braze material. The tip attachment PSP  150  is preferably no more than 250 microns thick and is produced at a similar temperature as the PSP replacement tip  140  described above but is held at temperature for a shorter period of time (less than 15 minutes). The tip attachment PSP  150  therefore has enough unreacted braze material to be able to join the replacement tip  140  to the blade  30  being repaired as illustrated in  FIG. 19 , regardless of how the replacement tip  140  is manufactured (PSP or additive manufacturing). 
     The replacement tip  140  has sufficient mechanical properties and oxidation resistance due to the adjusted composition and the Ni—Cr—(Ti, Zr, Hf) braze composition. 
     As discussed earlier, gas turbine components operate under a variety of localized conditions that can produce localized damage. This can be attributed to varied component conditions (e.g., temperatures, pressures, fluid properties, etc.) and engine conditions. 
     One example of localized operating conditions exists at the row one turbine blade  155  where localized distress on the blades  155  can cause damage in multiple areas including a leading edge  160  of the blade  155  and a tip  165  of the blade  155 .  FIG. 22  illustrates the leading edge  160  and the tip  165  of the blade  155  and also illustrates a replacement tip  170  installed to repair cracking and/or oxidation damage at the blade tip  165 . 
     One type of damage occurs at the leading edge  160  of the first stage blade  155 , as well as other blades where the ceramic coating adheres adjacent a series of cooling apertures  175 . If the coating spalls, a leading edge burn out or loss is often observed. The other area where damage can occur is at the tip  165  of the blade  155  where the blade  155  can rub against a ring segment or other component radially outward of the blade  155 . Heavy oxidation can also occur at the tip  165  of the blade  155  and cracks or tip cracks can form and propagate from cooling apertures  175  or from damage caused by other factors such as rubbing or oxidation. 
     As discussed previously, repairs to blade or vane tips  165  can include the removal of a portion of the blade tip  165  followed by replacement with a replacement tip  170 . Similar repairs can also be made to blade or vane leading edges  160 . 
     Additive manufacturing can be relied upon to manufacture replacement components or replacement tips  170  with brazing processes and special braze materials enhancing the operation of the repaired vane or blade  155 . 
     One preferred additive manufacturing process well-suited to manufacturing replacement components or replacement tips  170  includes atomic diffusion.  FIGS. 20-22  illustrate the process of repairing the blade tip  165  using atomic diffusion to form the replacement tip  170 . As one of ordinary skill will realize, the same process could be applied to the repair of the leading edge  160  of the blade  155  or vane as well as to other components not discussed herein. 
     With reference to  FIG. 20 , atomic diffusion uses binding agents and a metal powder for rapid construction of a 3D shape. The metal powder is generally selected to closely match the material (e.g., CM 247 LC superalloy) used in the component (i.e., the blade  155 ) being repaired. The metal powder and the polymeric binding agent are mixed and then formed into the desired shape that will ultimately result in the replacement component or tip  170 . This preliminary component  185  is often referred to as a “green-form”. The “green-form” component  185  is then heated and sintered in a high temperature sintering operation to remove the binding agent and mechanically/metallurgically bond the powder particles. The sintering temperature is selected to fully remove the binding agent while providing the desired mechanical/metallurgical bond of the powdered metal without fully melting the powdered metal particles. 
     One method of forming the green-form component  185  includes a 3-D printing technique. A wire feedstock is prepared including the desired powder metal and the binder. The user is able to combine material chemistries or tailor chemistries as desired to achieve the desired material properties in the completed replacement tip  170  or replacement piece. In addition, different compositions can be used at different times during the forming of the replacement tip  170  to achieve different properties at the different locations within the replacement tip  170 . For example, in one construction a composition intended to be a first or interfacing layer includes the desired base materials as well as braze material integrated into the wire feedstock. 
     To manufacture the replacement tip  170  or another component, the first or interfacing layer is deposited onto a support structure  190  or is formed independent of the support structure  190 . The first surface in the example of  FIG. 20  is intended to be the surface that interfaces or is brazed to the component being repaired (i.e., the blade  155 ) to attach the replacement tip  170  to the blade  155  being repaired. Additional layers may be formed on top of the first layer using the same material, or another material may be used as may be required for the particular replacement component. 
     For example, the feedstock could be changed to a second material that does not include the braze material and rather, more closely matches the base material of the blade  155  or other component being repaired. As discussed above, some materials could be employed that enhance the performance of the replacement tip  170  or other component over that of the base material. Any of those materials could be employed in this process as well. For example, up to 8% aluminum could be employed to enhance oxidation resistance. As previously noted, the sintering process is designed to not melt the powdered material. Because the process is a non-melting process, no variation in chemistry is expected. 
     With continued reference to  FIG. 20 , the metal powder is extruded with the binder (e.g., a polymer) to create the wire feedstock that is then deposited onto the support structure  190 . A ceramic interlayer  195  may be positioned between the deposited material and the support structure  190  to aid in the removal of the completed replacement tip  170  from the support structure  190 . A washing step of the green structure removes the polymer binder and densification is performed via sintering. Typically, densities of greater than ninety-six percent can be achieved but this is dependent on component size and corresponding wall thickness, since the densification is achieved by solid stage diffusion. Examples of replacement tips  170  formed using this process, after sintering and removed from the support structure are illustrated in  FIG. 21 . 
     This method does not experience the isotropy of layer-based AM techniques and because of its speed in producing the green-form component  185  and very low powder waste, reduces cost significantly over other AM techniques. In addition, as noted earlier this process of additive manufacturing can be used to form components other than replacement tips  170 , including leading edge replacements or other components and can include advanced features such as attachment structures  110 . 
     Another benefit with this approach is that the components can be made from other high temperature resistant materials (e.g., oxide dispersion strengthened (ODS) or advanced single crystal (CMSX8/René N5/PWA1484)) that have better strength, oxidation resistance, and coating adhesion. 
     In summary,  FIGS. 20-22  illustrate a replacement tip  170  during various states of manufacture using the atomic diffusion process. After removal of the damaged portion of the tip  165  of the blade  155  being repaired, the replacement tip  170  can be sized for manufacture. In many cases, the support structure  190  will be needed to define a base of support onto which the replacement tip  170  can be formed. While not required, in situations where the support structure  190  is used, a ceramic interlayer  195  may be first applied to aid in easily separating the completed replacement tip  170  from the support structure  190 . 
     The green-form component  185  is next printed using feedstock of the appropriate makeup. The first layer, or the first few layers may use a feedstock that is part base material, part binder, and part braze material that ultimately is used during the attachment of the replacement tip  170  to the blade  155 . After these initial layers are printed, the feedstock may be switched to a feedstock that includes the desired base metal chemistry (i.e., a chemistry closely matching the blade  155 ) and a binder, often in the form of a polymer. The chemistry of the subsequent feedstock may include an enhanced chemical make-up as discussed earlier to provide superior material properties such as oxidation resistance. 
     Upon completion of the 3-D printing process, the green-form component  185  is washed and sintered to remove the binder and to mechanically or metallurgically bond the remaining particles in the desired shape. The sintered replacement tip  170  is removed from the support structure  190  as illustrated in  FIG. 21 . 
     As illustrated in  FIG. 22 , the replacement tip  170  is placed in position on the blade  155  and a braze joint  200  is formed therebetween. During the brazing process, braze material in the initial layer or layers of the replacement tip  170  facilitates the completion of the braze joint and the attachment of the replacement tip  170 . 
     Current materials used for pre-sintered preforms (PSPs) and for brazing materials for use with nickel-base super alloy materials that operate in high temperature environments (e.g., 1000 degrees F., 538 degrees C.) are typically nickel (Ni) chromium (Cr) based. 
     The composition described herein is preferably applied to PSPs and/or braze materials that do not include boron. To improve the creep rupture life of boron-free PSPs and braze materials, rhenium (Re) or Ruthium (Ru) can be added to most nickel-base braze alloys. These two elements are potent creep resistance elevators that are added to base metal composition for creep-rupture life improvement. They increase the creep resistance of nickel-base alloys by up to a factor of ten. Their high melting point and large atomic diameter results in low atomic diffusion rates and enables Ni base materials to increase their creep resistance. 
     Rhenium (Re) and Ruthium (Ru) have not been added to boron-free braze materials to date as the need for creep resistance braze materials was not known. 
     To add Re or Ru, the materials are powdered and then mixed with a base material powder mixture prior to brazing. Re and Ru are added to boron free Ni—Cr—X braze/base material powder mixture prior to PSP making. Preferably, the Re and Ru have the smallest particle size possible for the powder. It is preferred that Re and Ru powder diameter is at least 50% or smaller than the base metal and braze metal powder to assure uniform mixing and homogeneous elemental distribution after brazing. Re and Ru powders are not melted during the brazing process. Rather they diffuse into the surrounding liquid braze material during braze. Since diffusion rates are high in liquid, these elements are transported uniformly within the braze material. 
     Re and Ru are added such that they make up 3-6 percent of the total composition of the braze or PSP regardless of the proportion of base metal to braze powder in the braze. 
     For example, the repair of a component manufactured from CM 247 LC superalloy may employ a PSP that is manufactured from powders in which 74-77 percent matches the CM 247 LC superalloy composition, 20 percent matches a desired braze material (sometimes referred to as a melting point depressant), and 3-6 percent is one or both of Re or Ru. 
     Suitable braze materials are typically nickel-base and include nickel, chromium, and at least one of titanium, zirconium, and hafnium. Some specific braze compositions include a composition that includes 6.5% Cr, 11% Zr, 7.5% Ti, and the remainder Ni. Another composition could include 5.0% Cr, 10% Hf, 10% Zr, and the remainder Ni. Yet another composition could include 17% Cr, 22% Ti, and the remainder Ni. 
     Each of the three components, the base material (74-77 percent), the braze material (20 percent), and the Re or Ru (3-6 percent) are powdered and mixed together for sintering. During any melting steps (i.e., brazing processes), the Re and Ru are not melted. Rather, they disperse through any melt pools during the melting process. 
       FIG. 3  illustrates one possible PSP insert  60  that could be manufactured using the above-described materials. The PSP insert  60  is preformed and sintered to include base material, a braze material, and the desired quantity of Re or Ru.  FIG. 4  illustrates the repair of a turbine vane  30  using the PSP insert  60  illustrated in  FIG. 3 . After the damaged portion of the vane  30  is removed, the required PSP insert  60  is sized and manufactured as described. The PSP insert  60  is then positioned in the empty space  55  in the vane  30  and brazed into place. During the brazing process, some of the Re and Ru will migrate into the liquid braze. The Re and Ru will not melt in the pool but rather will become embedded in the braze material during solidification. 
     Nickel-base superalloys that include more than about two percent aluminum are known to be particularly difficult to weld or to form using present additive manufacturing techniques. Components, parts of components, or preforms using these materials can be manufactured using a process similar to that described above. In one example, a preform (e.g., preforms  105 ,  250 , etc.) with a nickel-base superalloy that may include at least 4.5 percent aluminum is formed. Of course, the system and process can be used with virtually any desired material. In one process, illustrated in  FIG. 26  a pre-sintered preformed (PSP), such as the one illustrated in  FIGS. 23-25  is formed for the repair or the manufacture of a component having a base material that is a nickel-base superalloy with more than 4.5% percent aluminum. To form the PSP a mixture of powdered base material, a braze material, and a binder is made (step  500 ). For gas turbine applications, a mixture of 80 percent base material and 20 percent braze material is suitable, with binder added as required to meet the requirements of the additive manufacturing process being employed (step  505 ). The mixture is made to be suitable for use in a micro-dispensing additive manufacturing system such as those used and sold by ηSCRYPT of Orlando Fla. (step  510 ). Micro-dispensing AM systems can dispense the mixture in layers that are as thin as 10 microns and as thick as 100 microns with preferred thicknesses being 20 microns to 50 microns. 
     The micro-dispensing AM system is then operated to dispense the mixture in a series of layers that define the desired shape of the PSP (step  515 ) (e.g., replacement piece  250 , PSP interface component  290 , etc.). Preferably, each layer is between 20 microns and 100 microns in thickness with other thicknesses being possible. The use of the micro-dispensing AM system allows for very fine control including the use of a CNC model to drive the positioning of the layers to improve the accuracy and finish of the final component. 
     Once the micro-dispensing AM process is completed, the component is removed from the device and is heated to a temperature less than 500 degrees C. but hot enough to remove the binder from the component (step  520 ). At the completion of this process, a component skeleton is formed that includes base material and braze material in the ratio selected for the mixture and gaps where the binder material was prior to its removal in the first heating process. 
     The component skeleton is then heated to a solid-state sintering temperature that for this material falls within the range of 1000 degrees C. to 1250 degrees C. (step  525 ). Typically, the solid-state sintering process requires less than 60 minutes to complete. Of course, other materials or mixtures having different ratios of the base material and braze material may have different solid-state sintering temperatures and may require more time to complete the solid-state sintering. 
     A second sintering process is then performed on the now sintered component skeleton (step  530 ). Specifically, the component is heated to a braze temperature greater than 1200 degrees C. such as a range of between 1250 degrees C. and 1300 degrees C. for less than 60 minutes to melt all or some of the braze material, but not the base material, thereby completing a liquid-phase sintering process. Of course, other materials or mixtures having different ratios of the base material and braze material may have different liquid-phase sintering temperatures and may require more time to complete the solid-state sintering. 
     To complete the formation of the skeleton component, the skeleton component is again heated to a solution treatment temperature range greater than 1200 degrees C. such as a range between 1230 degrees C. and 1300 degrees C. for between 1 and 12 hours to complete a homogenization/diffusion annealing process (step  535 ). Of course, other materials or mixtures having different ratios of the base material and braze material may have different diffusion annealing temperatures and may require more time to complete the diffusion annealing process. 
     Following these steps allows for the sintering of the component without melting and solidifying the base material (high γ′ forming nickel-base superalloy powder) such that the component is not prone to cracking. 
     One variation of the process just described, illustrated in  FIG. 27  utilizes a mixture of base material and binder with no braze material (step  540 ). The component is 3d printed using the micro-dispensing AM process described above. A second mixture containing a braze and binder mixture is then applied to some or all the outer surfaces of the completed component using the micro-dispensing AM process or another process if desired (step  545 ). The various heating processes described above are then performed. During the liquid-phase sintering process, the braze melts and infiltrates the base metal powder of the component. 
     In another variation, of the just-described process, the component is covered or partially covered with either a 100 percent braze material binder mixture or a base material powder, a braze material powder, and a binder mixture. The sintered skeleton is ultimately infiltrated by the braze to obtain a near 100 percent dense component. 
     In all the processes just described, the braze material is preferably one of a Ni—Cr—Ti or a Ni—Cr—Ti—Zr braze. In addition, the aforementioned processes generally allow for the avoidance of a HIP (Hot Isostatic Pressing) operation as the liquid phase infiltration results in a near 100 percent dense structure (typically at least 99.9 percent). 
     As discussed, the above processes can be used to form components using high γ′ forming superalloy powder which does not melt in this process such that residual stresses that cause cracking and may be created during solidification are not present. 
     The micro-dispensing AM process can produce layers having thicknesses as low as 10 microns. In addition, PSP components or panels can be built and used to join nickel and cobalt base alloys including Ni—Cr—Ti and Ni—Cr—Ti—Zr. In addition, these materials and the micro-dispensing AM process can be used to produce foils having a total thickness of 50 microns or less (e.g., PSP interface component  290 ). In addition, the micro-dispensing AM process allows for the production of near net shape components using high γ′ forming materials without cracking. While an 80/20 (base material/braze material) powder mix is preferred for gas turbine applications, some applications may include up to 30 percent braze material. 
     It should be noted that while the foregoing examples describe the formation of PSP components separate from the components being repaired, some repairs may include printing the PSP preform directly onto the component being repaired. Thus, the invention should not be limited to PSPs that are formed separate from the component they are being made to repair. 
     In addition, it should be appreciated that the braze material powders described herein may be used to produce superalloy components (or portions thereof) via other types of additive manufacturing and welding processes that use metal powders to build up parts, including selective laser melting (SLM), laser powder deposition (LPD), laser metal deposition (LIVID), directed energy deposition (DED), and laser wire deposition (LWD). In such embodiments the braze material powder may correspond to a eutectic powder that is mixed with a base material powder to form a superalloy powder mixture. This superalloy powder mixture may then be used by a 3D printer to produce a new part (or portion thereof). 
     As discussed previously, the base material powder (mixed with the braze/eutectic powder to form the superalloy powder mixture) may correspond to a nickel-base superalloy. Such a superalloy may include by weight greater than 40% nickel and greater than 4% in total of aluminum and optional titanium content. In particular, such a base material powder may comprise by weight about 4% to about 23% chromium, about 4% to about 20% cobalt, 0% to about 8% titanium, about 1.5% to about 8% aluminum, 0% to about 11% tungsten, 0% to about 4% molybdenum, 0 to about 13% tantalum, 0% to about 0.2% carbon, 0% to about 1% zirconium, 0% to about 4% hafnium, 0% to about 4% rhenium, 0% to about 0.1% yttrium and/or cerium, 0% to about 0.04% boron, 0% to about 2% niobium and balance nickel as its primary components. For example, the base material powder may correspond to or be similar to commercially available difficult-to-weld high γ′ prime forming superalloys with chemistries such as the CM 247 LC superalloy discussed previously or other commercially available superalloys such as those listed in the following Table I (as well as other superalloys). 
     
       
         
           
               
             
               
                 TABLE I 
               
             
            
               
                   
               
               
                 Superalloys (Wt % Element) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Alloy 
                 Cr 
                 Co 
                 Ti 
                 Al 
                 W 
                 Mo 
                 Ta 
                 C 
                 Zr 
                 Hf 
                 Re 
                 B 
                 Nb 
                 Ni 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 CM 247 LC 
                 8.3 
                 9.3 
                 0.8 
                 5.6 
                 9.5 
                 0.5 
                 3.2 
                 0.1 
                   
                 1.4 
                   
                   
                   
                 bal. 
               
               
                 René N2 
                 13 
                 7.5 
                   
                 6.6 
                 3.8 
                   
                 5 
                   
                   
                 0.15 
                 1.6 
                   
                   
                 bal. 
               
               
                 René N4 
                 9 
                 8 
                 4.2 
                 3.7 
                 6 
                 2 
                 4 
                 0.05 
                   
                   
                   
                 0.004 
                 0.5 
                 bal. 
               
               
                 René N5 
                 7 
                 8 
                   
                 6.2 
                 5 
                 2 
                 7 
                 0.05 
                   
                 0.2 
                 3 
                 0.004 
                   
                 bal. 
               
               
                 René 80 
                 14 
                 9.5 
                 5 
                 3 
                 4 
                 4 
                   
                 0.17 
                 0.03 
                   
                   
                 0.015 
                   
                 bal. 
               
               
                 René 108 
                 8.4 
                 9.5 
                 0.7 
                 5.5 
                 9.5 
                 0.5 
                 3 
                   
                   
                 1.5 
                   
                   
                   
                 bal. 
               
               
                 René 142 
                 6.8 
                 12 
                   
                 6.1 
                 4.9 
                 1.5 
                 6.4 
                 0.12 
                 0.02 
                 1.5 
                 2.8 
                 0.015 
                   
                 bal. 
               
               
                 PWA 1484 
                 5 
                 10 
                   
                 5.6 
                 6 
                 2 
                 9 
                   
                   
                 0.1 
                 3 
                   
                   
                 bal. 
               
               
                 PWA 1480 
                 10 
                 5 
                 1.5 
                 5 
                 4 
                   
                 12 
                 .05 
                   
                   
                   
                 0.003 
                   
                 bal. 
               
               
                 PWA 1483 
                 12.8 
                 9 
                 4 
                 3.6 
                 3.8 
                 1.9 
                 4 
                 .07 
                   
                   
                   
                 0.02 
                   
                 bal. 
               
               
                 Inconel 738 
                 16 
                 8.5 
                 3.4 
                 3.4 
                 2.6 
                 1.7 
                 1.7 
                 0.18 
                 0.05 
                   
                   
                 0.01 
                 0.9 
                 bal. 
               
               
                 Inconel 792 
                 12.4 
                 9 
                 4 
                 3.4 
                 3.8 
                 1.9 
                 3.9 
                 0.12 
                 0.05 
                   
                   
                   
                   
                 bal. 
               
               
                 Inconel 939 
                 22.5 
                 19 
                 3.7 
                 1.9 
                 2 
                   
                 1.4 
                 0.15 
                 0.09 
                   
                   
                 0.01 
                 1 
                 bal. 
               
               
                 Inconel 6203 
                 22 
                 19 
                 3.5 
                 2.3 
                 2 
                   
                 1.1 
                 0.15 
                 0.1 
                 0.8 
                   
                 0.01 
                 0.8 
                 bal. 
               
               
                 CMSX-6 
                 10 
                 5 
                 4.7 
                 4.8 
                   
                 3 
                 2 
                   
                   
                 0.1 
                   
                   
                   
                 bal. 
               
               
                 CMSX-11C 
                 14.9 
                 3 
                 4.2 
                 3.4 
                 4.5 
                 0.4 
                 5 
                   
                   
                 0.04 
                   
                   
                 0.1 
                 bal. 
               
               
                 Udiemt-720 
                 18 
                 15 
                 5 
                 2.5 
                 1.25 
                 3 
                   
                 0.03 
                 0.03 
                   
                   
                 0.033 
                   
                 bal. 
               
               
                 GTD 111 
                 14 
                 9.5 
                 4.9 
                 3 
                 3.8 
                 1.5  
                 2.8 
                 0.1 
                   
                   
                   
                 0.01 
                   
                 bal. 
               
               
                 GTD444 
                 9.8 
                 7.5 
                 3.5 
                 4.2 
                 6 
                 1.5 
                 4.8 
                   
                   
                 0.15 
                   
                   
                 0.5 
                 bal. 
               
               
                   
               
            
           
         
       
     
     It should also be appreciated that such base material powder superalloys may include additional components such as 0% to 1.5% option incidental elements and/or unavoidable impurities such as listed and subsequently described with respect to Table VII. Further, superalloys sold under each of the brand names or trademarks listed in Table IV may be supplied with chemistries that vary in weight percent from those listed. 
     In example embodiments, the additive manufacturing process may be carried out by successively depositing and fusing together layers of a superalloy powder mixture of the base material powder and the eutectic powder to build up an additive portion. For SLM type printers, such fusing may be carried out via a laser selectively melting portions of the superalloy alloy mixture deposited on a powder bed. For LIVID type printers, a welding wire may provide the superalloy powder which is melted by a laser to build up each layer. Such a weld wire may be comprised of a nickel or a nickel alloy foil sheath which includes therein the superalloy powder mixture. 
     When superalloys (in particular difficult-to-weld high γ′ forming superalloys with an aluminum content of at least 4.5% by weight) are used as the base material powder in the superalloy powder mixture, the additive manufacturing process may initially form an additive portion with extensive amounts of solidification cracks and pores. However, during subsequent heat treatment, portions of the additive portion formed from the eutectic powder in the superalloy mixture may have a sufficiently low solidus temperature that it is capable of at least partially liquefying and filling in solidification cracks and pores (referred to herein as crack healing) without degradation of the shape of the additive portion and without the need for a HIP operation to collapse such cracks and pores. 
     In an example embodiment, the superalloy powder mixture may be comprised of at least 76% by weight of the base material powder and at least 6% by weight of the eutectic powder, to build up an additive portion. The base material powder and eutectic powder may each have a nickel content by weight greater than 40%. The base material powder (as well as the additive portion formed from the described superalloy alloy powder mixture) may have an aluminum content by weight greater than 1.5%. In addition, the eutectic powder may have a solidus temperature that is more than 220° C. below the solidus temperature of the base material powder. Further, the eutectic powder may have a liquidus temperature below 1300° C. In example embodiments, the eutectic powder may be comprised of a Ni—Cr—Ti—Zr powder or a Ni—Cr—Ti powder or other eutectic powder with the previously described properties. 
     In a first example of this crack healing process, a base material powder corresponding to CM 247 LC superalloy and a Ni—Cr—Ti—Zr eutectic powder with the respective chemistries shown in Table II, were mixed together in about a 90:10 ratio by weight respectively, to form a superalloy powder mixture. In this example, the liquidus temperature of the Ni—Cr—Ti—Zr eutectic powder is about 1225° C. 
     
       
         
           
               
             
               
                 TABLE II 
               
             
            
               
                   
               
               
                 Crack Healing AM Process Examples 
               
            
           
           
               
               
               
            
               
                   
                 Base Material  
                 Braze / Eutectic powder  
               
               
                 Element 
                 Powder (Wt %) 
                 (Ni-Cr-Ti-Zr) (Wt %) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Cr 
                 8.3 
                 8.0 
               
               
                 Co 
                 9.3 
                 0 
               
               
                 Ti 
                 0.8 
                 7.0 
               
               
                 Al 
                 5.6 
                 0 
               
               
                 W 
                 9.5 
                 0 
               
               
                 Mo 
                 0.5 
                 0 
               
               
                 Ta 
                 3.2 
                 0 
               
               
                 C 
                 0.1 
                 0 
               
               
                 Zr 
                 0 
                 11.0 
               
               
                 Hf 
                 1.4 
                 0 
               
               
                 Re 
                 0 
                 0 
               
               
                 Y 
                 0 
                 0 
               
               
                 B 
                 0 
                 0 
               
               
                 Ni 
                 Balance 
                 Balance 
               
               
                   
               
            
           
         
       
     
     This superalloy powder mixture may be usable in this described crack healing additive manufacturing process to produce parts having operational characteristics (e.g., in a gas turbine) similar to casted CM 247 LC superalloy.  FIG. 28  shows an image  2800  of a cross-sectional cut from a sample block  2802  made with an SLM 3D printer using this example superalloy powder mixture (after heat treatment but without carrying out a HIP operation). 
     For comparison purposes to illustrate the crack healing aspects of this described embodiment,  FIG. 29  shows an image  2900  of a cross-sectional cut from a sample block  2902  made with a corresponding SLM 3D printer and process parameters using a single CM 247 LC superalloy powder. The cracking healing (after heat treatment), that occurred in the sample block  2802  shown in  FIG. 28  (and made from the described superalloy powder mixture) achieved sizes/volumes of cracks and pores that are substantially less than the cracks and pores illustrated in sample block of  FIG. 29  (made from a single CM 247 LC superalloy powder). It should be appreciated that the microstructure of the sample block  2902  includes extensive amounts of microcracking and pores (compared to sample block  2802 ), which makes it unsuitable for use in gas turbine guide vanes and blades without a subsequent HIP operation. 
     It should also be appreciated that CM 247 LC superalloy (as well as the other superalloys such as those listed in Table I) may have element weight percent&#39;s that vary depending on the source of the superalloy. For example, nominal ranges for the chemistry of CM 247 LC superalloy are shown in Table III: 
     
       
         
           
               
             
               
                 TABLE III 
               
             
            
               
                   
               
               
                 CM 247 LC Superalloy Example Chemistry and Nominal Ranges 
               
            
           
           
               
               
               
            
               
                 Element 
                 Sample Block (Wt %) 
                 Nominal Ranges (Wt %) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Cr 
                 8.3 
                 about 8.0-about 8.5, for example 8.05-8.35 
               
               
                 Co 
                 9.3 
                 about 9.0-about 9.5, for example 9.15-9.35 
               
               
                 Ti 
                 0.8 
                 about 0.6-about 0.9, for example 0.65-0.85 
               
               
                 Al 
                 5.6 
                 about 5.4-about 5.7, for example 5.55-6.65 
               
               
                 W 
                 9.5 
                 about 9.3-about 9.7, for example 9.45-9.55 
               
               
                 Mo 
                 0.5 
                 about 0.4-about 0.6, for example 0.45-0.55 
               
               
                 Ta 
                 3.2 
                 about 3.1-about 3.3, for example 3.15-3.25 
               
               
                 C 
                 0.1 
                 about 0.05-about 0.11, for example 0.06-0.11 
               
               
                 Zr 
                 0 
                 0-about 0.02, for example 0-0.016 
               
               
                 Hf 
                 1.4 
                 about 1.3-about 1.5, for example 1.35-1.45 
               
               
                 Re 
                 0 
                 0-about 0.05, for example &lt;0.001 
               
               
                 Y and/or Ce 
                 0 
                 0-about 0.01, for example &lt;0.001 
               
               
                 B 
                 0 
                 0-about 0.04, for example 0.00-0.016 
               
               
                 Ni and unavoidable impurities  
                 Balance 
               
               
                   
               
            
           
         
       
     
     Further alternative embodiments of the superalloy alloy powder mixture may be comprised of other types of base material powders that are similar to or vary from those listed in Table I. For example, the superalloy alloy powder mixture may be comprised of a base material powder having a chemistry similar to René 142, René N5, and PWA 1484 branded superalloys with the following example chemistry shown in Table IV: 
     
       
         
           
               
             
               
                 TABLE IV 
               
             
            
               
                   
               
               
                 A Superalloy Base Material Powder Example 
               
            
           
           
               
               
            
               
                 Element 
                 Wt % 
               
               
                   
               
               
                 Cr 
                 about 5-about 7.3, for example 6.0-7.3 
               
               
                 Co 
                 about 7-about 13, for example 11.0-13.0, alternately for 
               
               
                   
                 example 7.0-9.0 
               
               
                 Ti 
                 0-about 0.05, for example 0 
               
               
                 Al 
                 about 5.5-about 6.5, for example 5.8-6.5 
               
               
                 W 
                 about 4.7-about 6, for example 4.7-5.2 
               
               
                 Mo 
                 about 1.2-about 2.2, for example 1.2-2.2 
               
               
                   
                 0-about 4.5, for example 0-4.0, alternatively for example less 
               
               
                 Ta 
                 than 3.5, alternatively for example less than 1.9, alternatively 
               
               
                   
                 for example 0-1.0, alternatively for example 0-0.05 
               
               
                 C 
                 0-about 0.15, for example 0.8-0.15 
               
               
                 Zr 
                 0-about 1, for example 0-0.05 
               
               
                 Hf 
                 0-about 1.7, for example 0-1.7 
               
               
                 Re 
                 about 2-about 4.2, for example 2.0-4.2 
               
               
                 Y and/or Ce 
                 0-about 0.1, for example 0.03-0.07 
               
               
                 B 
                 0-about 0.04, for example 0.0-0.016 
               
               
                 Ni and optional 
                 Balance 
               
               
                 incidental elements and unavoidable 
                   
               
               
                 impurities 
               
               
                   
               
            
           
         
       
     
     In these cracking healing examples, the heat treatment (during which crack healing occurs) may, for example, include a step of heating the sample block in a furnace above 1200° C. for at least 12 hours to homogenize the resulting crack healed alloy that forms the additive portion. The heat treatment process for this described crack healing additive manufacturing process may also include one or more heat treatment steps to achieve sufficient homogenization and high γ′ volume fractions (e.g., greater than 30%), such as those described previously. However, it should be appreciated that this cracking healing heat treatment may be carried out with more or less steps or different steps, temperatures, heating/cooling rates, and time ranges depending the extent of crack healing (and homogenization) that is needed for the particular part that is being produced and/or depending on chemistries of the particular base material powder and eutectic powder that were used to create the resulting alloy of the additive portion. 
     The following example chemistries shown in Table V of a Ni—Cr—Ti—Zr eutectic powder chemistry (when used to form a superalloy powder mixture in combination with a base material powder such as CM 247 LC superalloy illustrated in Table III, or other difficult-to-weld superalloys) may be capable of achieving the reductions in microcracking that were illustrated in the sample block  2802  shown in  FIG. 28 : 
     
       
         
           
               
             
               
                 TABLE V 
               
             
            
               
                   
               
               
                 Eutectic powder (Ni-Cr-Ti-Zr) Example Chemistries 
               
            
           
           
               
               
               
            
               
                   
                 Element 
                 Wt % 
               
               
                   
                   
               
               
                   
                 Cr 
                 about 6-about 11, for example 6.0-10.0 
               
               
                   
                 Co 
                 0-about 1, for example 0-1.0 
               
               
                   
                 Ti 
                 about 5-about 9, for example 5.0-9.0 
               
               
                   
                 Al 
                 0-about 1, for example 0-1.0 
               
               
                   
                 W 
                 0-about 1, for example 0-1.0 
               
               
                   
                 Mo 
                 0-about 0.55, for example 0-0.55 
               
               
                   
                 Ta 
                 0-about 1, for example 0-0.05 
               
               
                   
                 C 
                 0-about 0.08, for example 0-0.08 
               
               
                   
                 Zr 
                 about 9-about 13, for example 9.0-13.0 
               
               
                   
                 Hf 
                 0-about 0.05, for example 0.0-0.05 
               
               
                   
                 Re 
                 0-about 0.05, for example 0.0-0.05 
               
               
                   
                 Y and/or Ce 
                 0-about 0.1, for example 0-0.07 
               
               
                   
                 B 
                 0-about 0.04, for example 0.0-0.016 
               
               
                   
                 Ni and optional incidental 
                 Balance 
               
               
                   
                 elements and unavoidable 
                   
               
               
                   
                 impurities 
               
               
                   
                   
               
            
           
         
       
     
     Alterative embodiments may be carried out with a Ni—Cr—Ti Eutectic powder having a chemistry such as illustrated in the following Table VI: 
     
       
         
           
               
             
               
                 TABLE VI 
               
             
            
               
                   
               
               
                 Eutectic powder (Ni-Cr-Ti) Example Chemistries 
               
            
           
           
               
               
               
            
               
                   
                 Element 
                 Wt% 
               
               
                   
                   
               
               
                   
                 Cr 
                 about 15-about 19, for example 15.0-19.0 
               
               
                   
                 Co 
                 0-about 1, for example 0-1.0 
               
               
                   
                 Ti 
                 about 20-about 25, for example 20.0-25.0 
               
               
                   
                 Al 
                 0-about 1, for example 0-1.0 
               
               
                   
                 W 
                 0-about 1, for example 0-1.0 
               
               
                   
                 Mo 
                 0-about 0.55, for example 0-0.55 
               
               
                   
                 Ta 
                 0-about 1, for example 0-0.05 
               
               
                   
                 C 
                 0-about 0.08, for example 0-0.08 
               
               
                   
                 Zr 
                 0-about 1, for example 0-0.014 
               
               
                   
                 Hf 
                 0-about 0.05, for example 0.0-0.05 
               
               
                   
                 Re 
                 0-about 0.05, for example 0.0-0.05 
               
               
                   
                 Y and/or Ce 
                 0-about 0.1, for example 0-0.07 
               
               
                   
                 B 
                 0-about 0.04, for example 0.0-0.016 
               
               
                   
                 Ni and optional incidental 
                 Balance 
               
               
                   
                 elements and unavoidable 
                   
               
               
                   
                 impurities 
               
               
                   
                   
               
            
           
         
       
     
     It should be appreciated that these example Ni—Cr—Ti—Zr and Ni—Cr—Ti eutectic powder chemistries shown in Tables V and VI may also be used as braze materials for the other examples described herein. In addition, example embodiments of the superalloy chemistries described and claimed throughout this application may include one or more optional incidental elements and/or unavoidable impurities. In some example embodiments, the amount by weight of the total of any optional incidental elements may be between 0% and 1.5%. In further examples, the optional incidental elements may include one or more of the following in the indicated maximum amounts in weight % or ppm according to Table VII: 
     
       
         
           
               
             
               
                 TABLE VII 
               
             
            
               
                   
               
               
                 Optional Incidental Elements 
               
            
           
           
               
               
               
            
               
                   
                 Element 
                 Wt % or ppm (max) 
               
               
                   
                   
               
               
                   
                 S 
                 30 ppm 
               
               
                   
                 Nb 
                 1.5% 
               
               
                   
                 Mn 
                 0.6% 
               
               
                   
                 Fe 
                 0.05% 
               
               
                   
                 Si 
                 0.30% 
               
               
                   
                 P 
                 50 ppm 
               
               
                   
                 Mg 
                 50 ppm 
               
               
                   
                 Cu 
                 0.01% 
               
               
                   
                 N 
                 60 ppm 
               
               
                   
                 0 
                 250 ppm 
               
               
                   
                 Ag 
                 1 ppm 
               
               
                   
                 As 
                 5 PPm 
               
               
                   
                 Bi 
                 0.1 ppm 
               
               
                   
                 Cd 
                 2 ppm 
               
               
                   
                 Ga 
                 25 ppm 
               
               
                   
                 In 
                 0.2 ppm 
               
               
                   
                 Pb 
                 2 ppm 
               
               
                   
                 Sb 
                 2 ppm 
               
               
                   
                 Se 
                 1 ppm 
               
               
                   
                 Sn 
                 10 ppm 
               
               
                   
                 Te 
                 0.1 ppm 
               
               
                   
                 Tl 
                 0.2 ppm 
               
               
                   
                 Zn 
                 5 PPm 
               
               
                   
                 V 
                 1.5% 
               
               
                   
                   
               
            
           
         
       
     
     Also, in some example embodiments the amount by weight of the total of any unavoidable impurity elements may be between 0% and 0.01%. In further examples, unavoidable impurities may typically be within the maximum amounts listed in Table VII for these respective elements and for any other element that maximum may be about 0.001 in weight %. However, it should be appreciated that in further embodiments, one or more of such optional incidental elements and/or unavoidable impurities may exceed these described ranges, provided that such optional incidental elements and/or unavoidable impurities do not interfere with the ability of the described processes to produce additive portions with material properties after heat treatment (e.g., tensile strength, creep resistance) that meet the requirements for gas turbine hot gas path parts or other high temperature applications and are usable to replace corresponding parts made of an CM 247 LC superalloy or other hard-to-weld superalloys via casting processes. 
     Example embodiments may further include a methodology that facilitates additively manufacturing a superalloy component according to the example crack healing AM process described herein. The methodology may include an act of successively depositing and fusing together layers of a superalloy powder mixture comprised of a base material powder and a eutectic powder, to build up an additive portion. The eutectic powder has a solidus temperature lower than the solidus temperature of the base material powder. The methodology may also include an act of heat treating the additive portion at a temperature greater than 1200° C. to heal cracks and/or fill pores and to homogenize the alloy of which the additive portion is comprised. The additive portion alloy has a chemistry defined by the superalloy powder mixture. 
     In example embodiments, the base material powder may be a nickel-base superalloy with a nickel content by weight greater than 40% and with an aluminum content by weight of at least 1.5%. The eutectic powder may be a nickel-base alloy including by weight about 6% to about 11% chromium, about 5% to about 9% titanium, about 9% to about 13% zirconium, and greater than 40% nickel. 
     In example embodiments, the methodology may include an act of removing a damaged portion from a component to leave a first interface. The act of successively depositing and fusing together layers of the superalloy powder mixture may print a replacement portion that has a second interface surface. In addition, the methodology may include an act of attaching the second interface surface to the first interface surface to replace the damaged portion of the component. 
     In example embodiments of the methodology, heat treating may include heat treating the additive portion at a temperature at or above 1230° C. 
     In further examples, the ratio of the base material powder to the eutectic powder by weight in the superalloy powder mixture is between about 94:06 and about 76:24, and in particular between about 94:06 and about 85:15. 
     Also in example embodiments, at least 95% by weight of the additive portion alloy is formed from the base material powder and the eutectic powder. 
     In addition, the base material powder may include greater than 4% in total of aluminum and optional titanium content by weight. Further, the base material powder may include at least 4.5% aluminum by weight. Also, the eutectic powder may include at maximum 1% aluminum by weight. In addition, the base material powder may include at least 5.5% aluminum by weight and greater than 45% nickel by weight. 
     The balance of the eutectic powder by weight may include nickel and optional incidental elements and unavoidable impurities. The eutectic powder may include by weight at maximum 1.5% of one or more incidental elements. Also, the eutectic powder may include by weight at maximum 0.01% of one or more unavoidable impurities. 
     In addition, the solidus temperature of the eutectic powder may be more than 220° C. below the solidus temperature of the base material powder. Further, the eutectic powder may have a liquidus temperature below 1300° C. 
     In this example methodology, the additive portion alloy (after one or more heat treatments) has γ′ volume fractions greater than 30%, alternatively greater than 50%, and alternatively greater than 70%. 
     Further the additive portion may form at least a portion of a turbine blade or turbine guide vane. 
     In example embodiments, the superalloy powder mixture may be deposited and fused together via a SLM 3D printer to form the additive portion. 
     In alternative embodiments, the superalloy powder mixture may be deposited and fused together via a LWD system, which employs a welding wire to provide the superalloy powder mixture. The welding wire may be comprised of a nickel or a nickel alloy foil sheath including therein the superalloy powder mixture. 
     In addition, it should also be appreciated that this described methodology may include additional acts and/or alternative acts corresponding to the features described previously with respect to the crack healing process, braze materials, and other additive manufacturing processes described herein. 
     None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words “means for” are followed by a participle.