Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2001-05-30
2003-08-19
Koehler, Robert R. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C228S101000, C228S227000, C228S262700, C228S262800, C228S262900, C416S22300B, C416S24100B, C428S636000, C428S641000, C428S656000, C428S660000, C428S663000, C428S666000, C428S668000, C428S669000, C428S670000, C428S672000
Reexamination Certificate
active
06607847
ABSTRACT:
BACKGROUND OF THE INVENTION
This application generally relates to composite articles that are joined together using brazes. More particularly, the invention described herein relates to bonded niobium-based silicide and molybdenum-based silicide composite articles that are joined together using brazes.
Nickel (Ni)-based superalloys have been used as jet engine materials for many years. The surface temperatures at the hottest locations of state-of-the-art jet engine turbine airfoils now approach 1,150° C., which is approximately 85% of the melting temperatures of Ni-based superalloys. Niobium (Nb) and molybdenum (Mo) based refractory metal intermetallic composites (hereinafter referred to as “Nb-based RMICs” and “Mo-based RMICs,”) have much higher potential application temperatures, provided that they can be used at approximately 80% or more of their melting temperatures, which are generally greater than about 1700° C.
Complex silicide-based RMICs that are made from Nb—Si—Ti—Hf—Cr—Al alloys or Mo—Si—B—Cr alloys appear to have the potential to become the next generation turbine materials with a long term, high-temperature capability that is significantly higher than that of current Ni-based superalloys. Because of their high melting temperatures, however, direct casting of hollow engine components with cooling channels from these Nb- and Mo-based RMICs is expected to be very difficult. At such high temperatures, very few materials can serve as casting cores and molds without experiencing creep, cracking, or reactions with the molten metals and thus contaminating the melt and degrading the cores. One potential alternative technique for the manufacture of complex-shaped components (e.g. airfoils) with cooling channels is to bond together, typically using brazes, two or more structural members that have been machined to the appropriate shapes. Currently, however, no such braze materials exist for these Nb- and Mo-based RMICs.
It is known in the art to make hollow components, such as turbine blades, by joining and bonding halves or multiple pieces together. However, the prior-art braze materials that have been developed for Ni-based or Fe-based alloys are not suitable for use with the new Nb- and Mo-based RMICs, which have very different alloy compositions and much higher working temperatures. Detrimental interactions are known to occur between nickel brazes, for example, and Nb-based RMICs.
Accordingly, there is a need in the art for improved high temperature composite articles that are joined together using brazes.
BRIEF SUMMARY OF THE INVENTION
The present invention meets this and other needs by providing articles formed from Nb- and Mo-based RMICs that are joined together by a braze. Brazes for joining Nb- and Mo-based RMICs are also disclosed.
Accordingly, one aspect of the invention is to provide an article having a melting temperature of at least about 1500° C. The article comprises a first piece and a second piece joined by a braze to the first piece. The first piece comprises one of a first Nb-based RMIC and a first Mo-based RMIC, wherein the first Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the first Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron. The second piece comprises one of a second Nb-based RMIC and a second Mo-based RMIC, wherein the second Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the second Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron.
A second aspect of the invention is to provide an airfoil having a melting temperature of at least about 1500° C. The airfoil comprises a first piece and a second piece joined by a braze to the first piece. The first piece comprises one of a first Nb-based RMIC and a first Mo-based RMIC, wherein the Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the first Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron. The second piece comprises one of a second Nb-based RMIC and a second Mo-based RMIC, wherein said second Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the second Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron.
A third aspect of the invention is to provide an airfoil having a melting temperature of at least about 1500° C. and comprising a first piece and a second piece joined by a braze to the first piece. The first piece comprises one of a first Nb-based RMIC and a first Mo-based RMIC, wherein the Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the first Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron. The second piece comprises one of a second Nb-based RMIC and a second Mo-based RMIC, wherein the second Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the second Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron. The braze joining the first piece to the second piece comprises a first metallic element and a second metallic element, wherein the first metallic element is one of titanium, palladium, zirconium, niobium, and hafnium, the second metallic element is one of titanium, palladium, zirconium, niobium, hafnium, aluminum, chromium, vanadium, platinum, gold, iron, nickel, and cobalt, and wherein the first metallic element is different from the second metallic element.
A fourth aspect of the invention is to provide a turbine assembly having at least one component. The at least one component has a melting temperature of at least about 1500° C. and comprises a first piece and a second piece joined by a braze to the first piece. The first piece comprises one of a first Nb-based RMIC and a first Mo-based RMIC, wherein the Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the first Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron. The second piece comprises one of a second Nb-based RMIC and a second Mo-based RMIC, wherein the second Nb-based RMIC comprises titanium, hafnium, silicon, chromium, and niobium, and the second Mo-based RMIC comprises molybdenum, silicon, and at least one of chromium and boron. The braze joining the first piece to the second piece comprises a first metallic element and a second metallic element, wherein the first metallic element is one of titanium, palladium, zirconium, niobium, and hafnium, the second metallic element is one of titanium, palladium, zirconium, niobium, hafnium, aluminum, chromium, vanadium, platinum, gold, iron, nickel, and cobalt, and wherein the first metallic element is different from the second metallic element.
Finally, a fifth aspect of the invention is to provide a method of making an article having a melting temperature of at least about 1500° C. and comprising a first piece and a second piece that are joined together by a braze. The first piece and second piece each comprise one of a niobium based refractory intermetallic composite and a molybdenum silicide based composite, wherein the niobium based refractory intermetallic composite comprises titanium, hafnium, silicon, chromium, and niobium and the molybdenum silicide based composite comprises molybdenum, silicon, and at least one of chromium and boron. The method comprises the steps of: providing the first piece and the second piece such that the first piece and the second piece form a an interface therebetween; providing a braze to the interface between the first piece and the second piece, the braze having a melting temperature and comprising a first metallic element and a second metallic element, the first metallic element one of titanium, palladium, zirconium, niobium, and hafnium, and the second metal one of titanium, palladium, zirconium, niobium, hafnium, aluminum, chromium, vanadium, platinum, gold, iron, nickel, and cobalt, wherein the first metallic element is different from the second metallic element; heating the first piece, the second piece, and
Bewlay Bernard Patrick
Jackson Melvin Robert
Zhao Ji-Cheng
Johnson Noreen C.
Koehler Robert R.
Santandrea Robert P.
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