Fixture and method for resistance welding of a pad to a surface

A fixture and method for resistance welding of at least one pad to at least one surface of an article is disclosed. The method includes mounting the article in the fixture, placing the at least one pad on the at least one surface of the article, positioning a first electrode of a resistance welding apparatus to the at least one pad and a second electrode of the resistance welding apparatus to the article, and applying pressure and electric current across the at least one pad and the at least one surface. The fixture includes a first, second and third support element, which, respectively, include a first, second and third contact surface being adapted and disposed to support a first, second and third portion of the article. The first, second and third contact surfaces are each inelastic and electrically insulating. The fixture is arranged and disposed to non-rotatably cradle the article.

FIELD OF THE INVENTION

The present invention is directed to a fixture and a method for resistance welding. More particularly, the present invention is directed to a fixture and a method for resistance welding of a pad to a surface.

BACKGROUND OF THE INVENTION

Certain gas turbine blades have shrouds at the outer extremity of the airfoil. The blade shrouds are typically designed with an interlocking feature, usually in the form of a notch, which allows each blade to be interlocked at its shroud with an adjacent neighbor blade when such blades are installed about the circumference of a turbine disk. This interlocking feature assists in preventing the airfoils from vibrating, thereby reducing the stresses imparted on the blades during operation.

Turbine blades are often made of nickel-based superalloys or other high temperature superalloys designed to retain high strength at high temperature. The material of the blade shrouds and the interlocking notch may lack sufficient hardness to withstand wear stresses and rubbing which occur during start-up and shut-down of a turbine engine, as the shrouded blades twist to an “interlocked” and “non-interlocked” position, respectively. Due to the relatively low Rockwell hardness of the typical materials of the blade shrouds and the interlocking notch, the interlocks may wear, resulting in gaps opening between the blade shrouds, thereby allowing the airfoils to twist and further deform, and even to possibly vibrate during operation which is highly undesirable as such imparts additional higher stresses on the blades which can quickly lead to blade breakage and consequent failure of the turbine.

BRIEF DESCRIPTION OF THE INVENTION

In an exemplary embodiment, a fixture for resistance welding of at least one contact pad to at least one intershroud contact surface of a shrouded turbine blade includes a first support element, a second support element and a third support element. The first support element includes a first contact surface, the first support element being adapted and disposed to support a shroud edge of the shrouded turbine blade, and the first contact surface being inelastic and electrically insulating. The second support element includes a second contact surface, the second support element being adapted and disposed to support a root of the shrouded turbine blade, and the second contact surface being inelastic and electrically insulating. The third support element includes a third contact surface, the third support element being adapted and disposed to support an angel wing of the shrouded turbine blade, and the third contact surface being inelastic and electrically insulating. The fixture is arranged and disposed to non-rotatably cradle the shrouded turbine blade with the at least one intershroud contact surface accessible for placement of the at least one contact pad and application of a first electrode of a resistance welding apparatus to the at least one contact pad and a second electrode of the resistance welding apparatus to the shrouded turbine blade.

In another exemplary embodiment, a method for resistively welding at least one pad to at least one surface of an article includes mounting the article in a fixture, placing the at least one pad on the at least one surface of the article, positioning a first electrode of a resistance welding apparatus to the at least one pad and a second electrode of the resistance welding apparatus to the article, and applying pressure and electric current across the at least one pad and the at least one surface of the article. The fixture includes a first support element, a second support element, and a third support element. The first support element includes a first contact surface, the first support element being adapted and disposed to support a first portion of the article, and the first contact surface being inelastic and electrically insulating. The second support element includes a second contact surface, the second support element being adapted and disposed to support a second portion of the article, and the second contact surface being inelastic and electrically insulating. The third support element includes a third contact surface, the third support element being adapted and disposed to support a third portion of the article, and the third contact surface being inelastic and electrically insulating. The fixture is arranged and disposed to non-rotatably cradle the article.

In another exemplary embodiment, a method for resistively welding a first at least one contact pad to a first at least one intershroud contact surface of a shrouded turbine blade and a second at least one contact pad to a second at least one intershroud contact surface of the shrouded turbine blade includes mounting the shrouded turbine blade in a fixture, placing the first at least one contact pad on the first at least one intershroud contact surface, positioning a first electrode of a resistance welding apparatus to the first at least one contact pad and a second electrode of the resistance welding apparatus to the shrouded turbine blade, and applying pressure and electric current across the first at least one contact pad and the first at least one intershroud contact surface. The shrouded turbine blade is dismounted from the fixture, rotated, and remounted in the fixture. The second at least one contact pad is placed on the second at least one intershroud contact surface, the first electrode of the resistance welding apparatus is positioned to the second at least one contact pad and the second electrode of the resistance welding apparatus is positioned to the shrouded turbine blade, and pressure and electric current is applied across the second at least one contact pad and the second at least one intershroud contact surface. The fixture includes a first support element, a second support element and a third support element. The first support element includes a first contact surface, the first support element being adapted and disposed to support a shroud edge of the shrouded turbine blade, and the first contact surface being inelastic and electrically insulating. The second support element includes a second contact surface, the second support element being adapted and disposed to support a root of the shrouded turbine blade, and the second contact surface being inelastic and electrically insulating. The third support element includes a third contact surface, the third support element being adapted and disposed to support an angel wing of the shrouded turbine blade, and the third contact surface being inelastic and electrically insulating. The fixture is arranged and disposed to non-rotatably cradle the shrouded turbine blade.

DETAILED DESCRIPTION OF THE INVENTION

Provided are exemplary fixtures and a methods for resistance welding of a pad to a surface. Embodiments of the present disclosure, in comparison to methods not utilizing one or more features disclosed herein, increase efficiency, reduce costs, reduce process time, increase joint strength, or a combination thereof.

Referring toFIGS. 1 and 2, in one embodiment, a fixture100for resistance welding of at least one pad106to at least one surface104of an article102includes a first support element108, a second support element114, and a third support element120. The first support element108includes a first contact surface110, the first support108element being adapted and disposed to support a first portion112of the article102, and the first contact surface110being inelastic and electrically insulating. The second support element114includes a second contact surface116, the second support element114being adapted and disposed to support a second portion118of the article102, and the second contact surface116being inelastic and electrically insulating. The third support element120includes a third contact surface122, the third support element120being adapted and disposed to support a third portion124of the article102, and the third contact surface122being inelastic and electrically insulating. The fixture100is arranged and disposed to non-rotatably cradle the article102with at least one surface104of the article102accessible for placement of the at least one pad106on the at least one surface104and the application of a first electrode128of a resistance welding apparatus126to the at least one pad106and a second electrode130of the resistance welding apparatus126to the article102.

As used herein, “inelastic” indicates a material which does not exhibit any significant elasticity under the temperature and pressure conditions necessary for resistively welding the at least one pad106to the at least one surface104. As used herein, “non-rotatably cradle” indicates that the fixture100maintains the article102in place without significant translational or rotational movement under the physical conditions generated by the resistance welding apparatus126resistively welding the at least one pad106to the at least one surface104.

In one embodiment, the article102is a turbine component132. The turbine component132may be formed from any suitable material, including, but not limited to, superalloys, nickel-based superalloys, cobalt-based superalloys, or combinations thereof. In a further embodiment, the turbine component132is a shrouded turbine blade134including a root136, an airfoil138, a blade shroud140, and an angel wing142. The blade shroud140includes a shroud edge144, and at least one interlocking notch146having at least one intershroud contact surface148. The at least one intershroud contact surface148is the at least one surface104. The first portion112of the article102is the shroud edge144, the second portion118of the article102is the root136, and the third portion124of the article102is the angel wing142. The at least one pad106is at least one contact pad150.

The at least one pad106may include any suitable material, including, but not limited to, CM64, PWA 694, MTS 1087A, B50TF193, B50TF193S6, T800, or combinations thereof. In one embodiment, the at least one pad106includes a material having a diamond pyramid hardness of at least about 175 at 1,400° F. The at least one pad106may be free of low melt alloys and binding agents. As used herein, “free of low melt alloys and binding agents” indicates that any low melt alloy or binding agent present, cumulatively, is beneath the threshold which would materially affect the physical properties of the at least one pad106. In another embodiment, the at least one pad106is more resistive to abrasion than the at least one surface104of the article102. In yet another embodiment, the at least one pad106includes a thickness between about 0.005 inches and about 0.400 inches, alternatively between about 0.01 inches and about 0.35 inches, alternatively about 0.05 inches to about 0.30 inches, alternatively between about 0.10 inches to about 0.25 inches.

The fixture100may be configurable for resistance welding of a first at least one pad152to a first surface154of the article102and a second at least one pad156to a second at least one surface158of the article102.

In one embodiment, the fixture100is arranged and disposed to position the article102with at least three distinct welding positions accessible on the at least one pad106.

The fixture100may include at least one point of contact with a supporting surface160. The fixture100may further include at least four points of contact with the supporting surface160.

In one embodiment, a method for resistively welding at least one pad106to at least one surface104of an article102includes mounting the article102in the fixture100, placing the at least one pad106on the at least one surface104of the article102, positioning a first electrode128of a resistance welding apparatus126to the at least one pad106and a second electrode130of the resistance welding apparatus126to the article102, and applying pressure and electric current across the at least one pad106and the at least one surface104of the article102. Resistively welding the at least one pad106to the at least one surface104may include resistively welding the at least one pad106to the at least one surface104in at least three distinct locations.

In a further embodiment, mounting the article102in the fixture100includes mounting a shrouded turbine blade134in the fixture100. Placing the at least one pad106on the at least one surface104of the article102may include placing the at least one pad106on at least one intershroud contact surface148of the shrouded turbine blade134. Mounting the article102in the fixture100may further include disposing a shroud edge144of the shrouded turbine blade134on the first contact surface110of the first support element108, disposing a root136of the shrouded turbine blade134on the second contact surface116of the second support element114, and disposing an angel wing142of the shrouded turbine blade134on the third contact surface122of the third support element120.

In another embodiment, a method for resistively welding a first at least one pad152to a first at least one surface154of an article102and a second at least one pad156to a second at least one surface158of the article102includes mounting the article102in the fixture100, placing the first at least one pad152on the first at least one surface154, positioning a first electrode128of a resistance welding apparatus126to the first at least one pad152and a second electrode130of the resistance welding apparatus126to the article102, applying pressure and electric current across the first at least one pad152and the first at least one surface154, dismounting the article102from the fixture100, rotating the article102, remounting the article102in the fixture100, placing the second at least one pad156on the second at least one surface158, positioning the first electrode128of the resistance welding apparatus126to the second at least one pad156and the second electrode130of the resistance welding apparatus126to the article102, and applying pressure and electric current across the second at least one pad156and the second at least one surface158. Resistively welding the first at least one pad152to the first at least one surface154may include resistively welding the first at least one pad152to the first at least one surface154in at least three distinct locations. Resistively welding the second at least one pad156to the second at least one surface158may include resistively welding the second at least one pad156to the second at least one surface158in at least three distinct locations. The identification of the first at least one pad152and the first at least one surface154, and the second at least one pad156and the second at least one surface158, inFIGS. 1 and 2are for illustrative purposes only, and are considered to be interchangeable.

The fixture100may be reconfigured from a first contract surface configuration to a second contact surface configuration to non-rotatably cradle the article102with the first at least one surface154accessible for placement of the first at least one pad152on the first at least one surface154and the application of the first electrode128to the first at least one pad152and the second electrode130to the article102prior to rotating the article102, and to non-rotatably cradle the article102with the second at least one surface158accessible for placement of the second at least one pad156on the second at least one surface158and the application of the first electrode128to the second at least one pad156and the second electrode130to the article102after rotating the article102.