Abstract:
A system, process, and component are disclosed. The system and process involve an induction heater arranged and disposed to heat a component to form a heated surface and a nozzle arrangement positioned to apply a fluid to the heated surface to form a processed surface of a component. The processed surface includes compressive residual stress resulting in increased resistance to fatigue, including fretting fatigue, for the component.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed to systems and methods of manufacturing and treating metal components. More specifically, the present invention is directed to systems and methods of inductively heating and applying fluid to metal components. 
       BACKGROUND OF THE INVENTION 
       [0002]    Metal components, such as compressor blade dovetails of gas turbines, are prone to failure by both fatigue and fretting fatigue. Fatigue can be described as the process by which cyclic loads below a material&#39;s tensile strength initiate and propagate surface cracks. Fretting fatigue can be described as a specific form of fatigue in which small amplitude sliding motion, for example, between about 50 and about 200 micrometers, initiates and propagates cracks. The sliding motion can exacerbate the usual fatigue process through production of abrasive, oxidized wear product. Fretting fatigue can occur in components such as aerofoil dovetails and/or the attachment points in gas or steam turbine rotors. Both ordinary and fretting fatigue cracks are surface-initiated microcracks that propagate to the interior of the component. When components have high temperature gradients with the surface being at a greater temperature than the interior portions, fretting fatigue cracks are more likely to be formed. Compressive residual stress proximal to the surface of the components reduces the likelihood that both fatigue and fretting fatigue cracks will form. 
         [0003]    In a known system, laser shock processing can be used to improve the fretting fatigue resistance by increasing compressive residual stress at the surface of a component. Using laser shock processing suffers from several drawbacks. For example, laser shock processing can damage components such as blade dovetails due to high intensity shock waves generated. The shock waves reflect on surfaces of the base material generating a tensile stress. The tensile stress can propagate existing flaws and cracks leading to failure of the base material. In addition, laser shock processing adds undesirable costs. 
         [0004]    In another known system, a coating is applied to a compressor blade dovetail to improve the fretting fatigue resistance. Application of the coating suffers from several drawbacks. For example, application of the coating Alumazite can have a premature failure due to the tensile nature of stress at an interface between the coating and a base material (for example, a martensitic stainless steel such as an alloy including about 15.5% chromium, about 6.3% nickel, about 0.8% molybdenum, about 0.03% carbon, and a balance of iron). This can result in propagation of cracks into the base material when the coating spalls off cracks. This can reduce the corrosion resistance of the base material and permit crevice corrosion of the base material. In addition, the coating can result in additional undesirable costs. 
         [0005]    In another known system, water jet impact is used to treat a component. The water jet impact removes debris and cleans the surface of the component. Water jet impact suffers from several drawbacks. For example, water jet impact does not improve fretting fatigue resistance and water jet impact does not increase the compressive residual stress near the surface of the component. 
         [0006]    A system and method capable of improving the fretting fatigue resistance of a component that does not suffer from the above drawbacks would be desirable in the art. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    According to an embodiment, a surface treatment system includes an induction heater arranged and disposed to heat a component to form a heated surface while in an induction treatment mode, a nozzle arrangement positioned to apply a fluid to the heated surface of the component at a pressure above a cavitation pressure of the fluid to form a processed surface while in a fluid application mode. The processed surface includes compressive residual stress. 
         [0008]    According to another embodiment, a surface treatment process includes inductively heating a component by an induction heater thereby forming a heated surface and applying a fluid by a nozzle arrangement to the heated surface at a pressure above a cavitation pressure of the fluid thereby forming a processed surface. The processed surface includes compressive residual stress. 
         [0009]    According to another embodiment, a surface treated component includes a processed surface including compressive residual stress formed by being inductively heated to form a heated surface and applying a fluid to the heated surface. The processed surface includes resistance to fretting fatigue greater than an interior portion of the component or untreated surfaces. 
         [0010]    Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a perspective view of an embodiment of an exemplary surface treatment system according to the disclosure. 
           [0012]      FIG. 2  shows a perspective view of an embodiment of an exemplary surface treatment system according to the disclosure. 
           [0013]      FIG. 3  shows a perspective view of an embodiment of an exemplary surface treatment system according to the disclosure. 
           [0014]      FIG. 4  shows an enlarged sectioned perspective view taken in direction  4 - 4  in the exemplary surface treatment system of  FIG. 1 . 
           [0015]      FIG. 5  shows an enlarged sectioned perspective view taken in direction  5 - 5  in the exemplary surface treatment system of  FIG. 2 . 
           [0016]      FIG. 6  shows a perspective view of an embodiment of an exemplary surface treatment system according to the disclosure. 
           [0017]      FIG. 7  shows a perspective view of an embodiment of an exemplary surface treatment system according to the disclosure. 
           [0018]      FIG. 8  shows a perspective view of an embodiment of an exemplary surface treated component according to the disclosure. 
           [0019]      FIG. 9  shows a sectioned view along line  9 - 9  of the exemplary surface treated component in  FIG. 8 . 
           [0020]      FIGS. 10-12  show plots of temperature over time comparatively illustrating an exemplary surface treatment process according to the disclosure. 
       
    
    
       [0021]    Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Provided is a surface treatment system and surface treatment process capable of improving the fretting fatigue resistance of a metal component. The system and method increase compressive residual stress thereby improving fretting fatigue resistance. Embodiments of the present disclosure permit automation of inductive heating and water jet peening, increase the useful life of induction heaters, generate compressive residual stress proximal to a surface of the component, reduce or eliminate cracks or propagation of cracks below a surface of the component, and combinations thereof. 
         [0023]    According to the present disclosure, both “fatigue” and “fretting fatigue” are less likely. Therefore, as used hereinafter, the terms “fatigue” and “fretting fatigue” are used interchangeably in the context of the present disclosure. 
         [0024]    Referring to  FIGS. 1-2 , a system  100  includes an induction heater  102  and a nozzle arrangement  104 . The system  100  is configured to inductively heat a metal component  106 . The metal component  106  includes any suitable metal or metallic composition. For example, in various embodiments, the metal component  106  includes an alloy of any type, including, but not limited to, austenitic steel, steel/nickel alloys, martensitic/bainitic stainless steels, etc. In one embodiment, the component  106  includes an alloy of martensitic/bainitic stainless steel having by weight chromium of less than about 15%, nickel of less than about 5%, manganese of less than about 2%, and molybdenum of less than about 3%. In one embodiment, the component  106  is secured by hardware (not shown) to restrain movement of the component  106  during induction treatment mode and/or fluid application mode. 
         [0025]    During an induction heating mode, the component  106  is heated by the induction heater  102  forming a heated surface (described below with reference to  FIG. 9 ). Referring to  FIG. 1 , in one embodiment, the component  106  is heated in a chamber  108  of the induction heater  102 . In one embodiment, the induction heater  102  is positionable by positioning hardware (not shown) and/or positioning equipment (not shown). In one embodiment, the chamber  108  is generally cylindrical and formed by the induction heater  102  and the nozzle arrangement  104  being positioned in a coaxial relationship or a unitary relationship. In this embodiment, the component  106  or a portion of the component  106  is positionable within the chamber  108  and/or the system  100  is positionable around or proximal to the component  106  or a portion of the component  106 . 
         [0026]    In another embodiment, referring to  FIG. 2 , the component  106  is heated by being proximal to the induction heater  102  (for example, being positioned adjacent to the induction heater  102  or being within an external circumferential region  103  proximal to the induction heater  102 ). In this embodiment, an interior surface  107  of the component  106  is heated by the induction heater  102 . In one embodiment, the heated surface is then cooled or allowed to cool. 
         [0027]    Referring to  FIGS. 1-2 , the nozzle arrangement  104  is configured to apply a fluid to the component  106  or a portion of the component  106  during a fluid application mode. Similar to the induction heater  102 , in one embodiment, the nozzle arrangement  104  is capable of applying the fluid to the component  106  or a portion of the component  106  within the chamber  108 . In one embodiment, the nozzle arrangement  104  is positionable by positioning hardware (not shown) and/or positioning equipment (not shown). In one embodiment, the nozzle arrangement  104  is capable of applying the fluid to the component  106  or a portion of the component  106  proximal to the nozzle arrangement  104  (for example, being positioned proximal to the nozzle arrangement  104  or being positioned within the external circumferential region  103  proximal to the nozzle arrangement  104 ) as shown in  FIG. 2 . 
         [0028]    In one embodiment, the nozzle arrangement  104  includes one or more nozzles  105  (suitable nozzles include ultra-high pressure water jet nozzle for water jet peening or any other nozzle operable within the nozzle arrangement  104 ). The nozzle arrangement  104  applies the fluid to the metal component  106 . In one embodiment, nozzle parameters are adjustable and coordinated through use of a control program (not shown) operable in conjunction with any suitable computer. In one embodiment, one or more of the nozzles  105  are configured to operate at a predetermined pressure or predetermined pressure range (for example, above about 1360 bar, between about 2000 bar and about 3500 bar, between about 2000 bar and about 3700 bar, at about 3000 bar, or at about 3500 bar). In one embodiment, one or more of the nozzles  105  are configured to apply the fluid at a predetermined velocity or within a predetermined velocity range (for example, 250 m/min, 500 m/min, about 560 m/min, about 1120 m/min, between about 250 m/min and about 500 m/min, or between about 560 m/min and about 1120 m/min). 
         [0029]    In one embodiment, one or more of the nozzles  105  are positioned at a predetermined distance  109  or within a predetermined distance range from the component  106  (for example, about 0.25 mm, about 0.5 mm, about 2 mm, between about 0.5 mm and about 2 mm, between about 0.25 and about 0.5 mm) and/or at a predetermined distance  111  or within a predetermined distance range from other nozzles  105  (for example, about 0.6 cm, about 7.5 cm, about 15 cm, between about 0.6 cm and about 15 cm, between about 0.6 cm and about 7.5 cm). Referring to  FIGS. 4-5 , in one embodiment, the nozzles  105  are oriented at a predetermined angle  115  or within a predetermined range of angles (for example, about 75 degrees, about 90 degrees, or between about 75 and 90 degrees). 
         [0030]    Although  FIGS. 1-2  show a substantially cylindrical geometry, the system  100  is capable of being any suitable geometry. For example, as shown in  FIG. 3 , in one embodiment, the system  100  is a substantially planar shape similar to a paddle. In other embodiments, the system  100  is substantially cuboid, substantially linear, shaped corresponding to the metal component  106  (for example, corresponding to the geometry of a compressor blade, a compressor dovetail, or a rotor), or combinations thereof. 
         [0031]    The induction heater  102  includes one or more induction coils  110 . Referring to  FIGS. 1 and 4 , in one embodiment, the induction coil  110  is oriented in a substantially helical arrangement within the system  100 . In one embodiment, the induction coil  110  is housed within an outer wall  302  (substantially forming an outer cylinder) and an inner wall  304  (substantially forming an inner cylinder). The nozzle arrangement  104  is positioned on or within the outer wall  302  (see  FIGS. 2 and 4 ), the inner wall  304  (see  FIGS. 1 and 3 ), or both. Referring to  FIG. 4 , in one embodiment, the coil  110  includes a fluid passage  112  to transport the fluid and transfer heat from the induction heater  102  to the fluid, thereby extending the usable life of the induction heater  102 . The fluid enters the fluid passage  112  through an inlet (not shown), cools the interior of the coil  110 , and exits the fluid passage  112  through an outlet (not shown) during the induction heating mode. In one embodiment, during induction heating mode, the fluid is collected, cooled, and re-circulated through the coil(s)  110 . During fluid application mode, a valve (not shown) directs a portion or all of the fluid through the nozzle arrangement  104  to be applied to the component  106 . In one embodiment, during fluid application mode, the fluid is collected, purified, and re-circulated. 
         [0032]    In one embodiment, the fluid is applied during fluid application mode under supercavitation conditions (for example, the fluid is at a temperature of about the boiling point of the fluid or a temperature corresponding to a cavitation pressure of the fluid). Supercavitation is the use of cavitation effects to create a bubble of gas inside of the fluid, allowing an object suspended in the fluid to travel at extremely high velocities due to the object being fully enclosed by the bubble. The supercavitation reduces drag on the object (for example, by about 1,000 times) allowing the object to be applied to the component  106  at the predetermined velocity range. In one embodiment, the object suspended in the fluid is an abrasive. A suitable fluid is water. A suitable abrasive is silicon carbide or ice having, for example, a substantially spherical geometry and/or a predetermined particle size or particle size range (for example, about 80 mesh, about 400 mesh, or between about 80 mesh and about 400 mesh). 
         [0033]    In one embodiment, as shown in  FIG. 6 , the system  100  includes the fluid passage  112  leading to the nozzle arrangement  104 , the fluid passage  112  and the nozzle arrangement  104  being proximal to the coil  110 , and the fluid passage  112  and the nozzle arrangement  104  being separate from the coil  110 . In this embodiment, the coil  110  is not cooled by the fluid and the system  100  is capable of being positioned such that the nozzle arrangement  104  and the coil  110  are proximal to the component  106  or a portion of the component  106 . In this embodiment, the fluid enters the fluid passage  112  through an inlet  602 , cools the interior of the coil  110 , and exits the fluid passage  112  through an outlet  604  during the induction heating mode. During fluid application mode, the fluid enters the fluid passage  112  through the inlet  602  and is applied to the component  106  through the nozzle arrangement  104 . The adjustment between the induction heating mode and the fluid application mode is achieved by any suitable mechanism including, but not limited to, a flow control mechanism such as a valve. 
         [0034]    In another embodiment, as shown in  FIG. 7 , the system includes the coil  110  being wrapped around the fluid passage  112  that leads to the nozzle arrangement  104 . In this embodiment, the coil  110  is cooled by the fluid passage  112  and the system  100  is capable of being positioned such that the nozzle arrangement  104  and the coil  104  are proximal to the component  106  or a portion of the component  106 . In this embodiment, the fluid enters the fluid passage  112  through an inlet  602 , cools the interior of the coil  110 , and exits the fluid passage  112  through an outlet  604  during the induction heating mode. During fluid application mode, the fluid enters the fluid passage  112  through the inlet  602  and is applied to the component  106  through the nozzle arrangement  104 . The adjustment between the induction heating mode and the fluid application mode is achieved by any suitable mechanism including, but not limited to, adjusting the nozzle arrangement  104  to prevent application of the fluid. 
         [0035]    Referring to  FIGS. 8-9 , in one embodiment, the component  106  is a turbine blade. The surface  116  of the turbine blade is heated by the induction heater  102  described above forming the heated surface. A sub-layer  902  of the component  106  defined by a predetermined depth  114  operates as a transition zone and is heated to a lesser degree by the induction heater  102  than the surface  116 . An interior portion  120  of the component  106  is heated to an even lesser degree or is substantially unaffected by the induction heating. Similarly, an untreated portion  904  is heated to a lesser degree or substantially unaffected by the induction heating. In an exemplary process, the component  106  is heated by the induction heater  102  (for example, on the surface  116  of the component  106 ). The inductive heating forms a compressive residual stress layer (for example, on the surface  116  of the component  106 ). In one embodiment, the compressive residual stress formed (for example, extending to the predetermined depth  114 ) is adjusted by increasing or decreasing the AC current frequency, the current density, the coil surface area, a distance between the coil  110  and the component  106 , other suitable parameters, or combinations thereof. 
         [0036]    AC current travels through the coil(s)  110  at a predetermined frequency and a predetermined current density. In one embodiment, the frequency is decreased and/or the current density is increased to decrease heating (for example, of the predetermined depth  114 ) in comparison to another portion of the component  106  (for example, the surface  116  of the component  106 ). In one embodiment, the AC current is adjustable from a first predetermined frequency (for example, about 100 kilohertz) to a second predetermined frequency (for example, about 1 megahertz) and/or the current density is adjustable from a first predetermined current density (for example, about 15×10 6  amp/m 2 ) to a second current density (for example, about 5×10 6  amp/m 2 ). 
         [0037]    Referring to  FIGS. 10 and 11 , a increase in the frequency (for example, to 1000 kilohertz as shown in  FIG. 10  from 100 kilohertz as shown in  FIG. 11 ) increases temperature at the surface  116 . This reduces heating at the predetermined depth  114  and a temperature increase is localized to the surface  116  of the metal component  106  while heating of an interior portion  120  is reduced or eliminated. Referring to  FIGS. 10 and 12 , an increase in current density (for example, from 5×10 6  amp/m 2  as shown in  FIG. 12  to 15×10 6  amp/m 2  as shown in  FIG. 10 ) increases temperature at the surface  116  in a substantially uniform manner. The relationships of these adjustments and/or the other adjustments described below are used for controlling the relative temperature, and thus the compressive residual stress, for the surface  116 , the predetermined depth  114 , the interior portion  120 , other suitable portions of the component  106 , and combinations thereof. 
         [0038]    Referring again to  FIGS. 1-2 , in one embodiment, a distance  113  between the metal component  106  and the induction heater  102  (or the coil(s)  110 ) is adjustable. For example, in one embodiment, the distance  113  between the induction heater  102  (or the coil(s)  110 ) and the component  106  is increased thereby forming a greater temperature gradient between the surface  116  (see  FIG. 9 ), the predetermined depth  114  (see  FIG. 9 ), the interior portion  120  (see  FIG. 9 ), and combinations thereof, thereby increasing compressive residual stress. In one embodiment, the coil  110  is positionable from a first position having a first predetermined cross-sectional area (for example, about 15 cm 2 ) to a second position having a second predetermined cross-sectional area (for example, about 225 cm 2 ). 
         [0039]    While only certain features and embodiments of the invention have been shown and described, many modifications and changes may occur to those skilled in the art (for example, variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (for example, temperatures, pressures, etc.), mounting arrangements, use of materials, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the claimed invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.