Patent Publication Number: US-2022212296-A1

Title: System and method for repairing high-temperature gas turbine blades

Description:
TECHNICAL FIELD 
     The present disclosure is directed, in general, to a system and method for repairing high-temperature gas turbine components, and more specifically to such a system and method for the repair 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 content makes the process unsuitable for large scale manufacturing or repair. In particular, attempts to additively manufacture components using Alloy (CM) 247, 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 
     A blade for a gas turbine includes a removed portion space, and further includes an airfoil portion defining the removed portion space, the airfoil portion formed from a base material, and a replacement component formed to fill the removed portion space. The replacement component is formed from a material that includes 50%-80% base material, 0%-30% braze material, and 0%-8% aluminum. A braze joint is formed between the airfoil portion and the replacement component to attach the replacement component to the airfoil portion and fill the removed portion space. 
     In another construction, a method of repairing a blade for a gas turbine formed from a nickel-based superalloy includes removing a portion of an airfoil portion of the blade to define a removed portion space, forming a replacement component sized to fill the removed portion space, the replacement component formed from a material that includes, greater than 50% base material that matches a material used to form the airfoil portion of the blade, and up to 8% aluminum. The method further includes brazing the replacement component to the airfoil portion using a braze material, the brazing step maintaining the temperature of the airfoil portion and the replacement component below a grain boundary melting temperature of the base material. 
     In another construction, a method of repairing a blade for a gas turbine formed from a nickel-based superalloy includes removing a portion of an airfoil portion of the blade to define a removed portion space, preparing a powdered metal and binder mixture, and forming a green-form component using the mixture. The method further includes heating the green-form component to burn out the binder, the powdered metal forming mechanical or metallurgical bonds to maintain the shape of the green-form component and sintering the green-form component to produce a replacement component having a density of at least 96 percent. In addition, the method includes positioning the replacement component in the removed portion space, the replacement component filling the removed portion space, and brazing the replacement component to the airfoil portion using a braze material, the brazing step maintaining the temperature of the airfoil portion and the replacement component below a grain boundary melting temperature of the base material. 
     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 . 
     
    
    
     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-based superalloy such as Alloy (CM)  247 .  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-based 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 gamma prime nickel 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-based 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-based 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-based gas turbine components, specifically Alloy (CM)  247  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. 
     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. 
     For example,  FIGS. 15-19  illustrate a process similar to that just described but for the repair of the tip  120  of a nickel-based gas turbine vane  30  or blade, and specifically a vane  30  or blade made from Alloy 247 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 power is generally selected to closely match the material (e.g., Alloy (CM)  247 ) 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/Rene 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-based 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-based 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 Alloy 247 may employ a PSP that is manufactured from powders in which 74-77 percent matches the Alloy 247 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-based 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. 
     Although an exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form. 
     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.