Abstract: An electron beam physical vapor deposition (EBPVD) apparatus and a method for using the apparatus to produce a coating material (e.g., a ceramic thermal barrier coating) on an article. The EBPVD apparatus generally includes a coating chamber that is operable at elevated temperatures and subatmospheric pressures. An electron beam gun projects an electron beam into the coating chamber and onto a coating material within the chamber, causing the coating material to melt and evaporate. An article is supported within the coating chamber so that vapors of the coating material deposit on the article. The operation of the EBPVD apparatus is enhanced by the shape and intensity of the electron beam pattern on the coating material and on a crucible containing the molten coating material.

Abstract: A thermal barrier coating (TBC) for a component intended for use in a hostile thermal environment. The TBC has an interior region and an outer surface region on and contacting the interior region. Both regions are formed of a ceramic material, with the interior region having a lower thermal conductivity than zirconia partially stabilized by about seven weight percent yttria. The interior region constitutes more than half of the thickness of the TBC, and the outer surface region constitutes less than half of the thickness of the TBC. The TBC has a columnar microstructure whereby the interior region and the outer surface region comprise columns of their ceramic materials. The outer surface region is more erosion and impact resistant than the interior region at least in part as a result of the columns thereof being more closely spaced than the columns of the interior region.

Abstract: An article and TBC coating system thereon that in combination exhibit significantly improved spallation resistance. The article comprises a substrate formed of a metal alloy containing ruthenium and one or more refractory elements (e.g., tantalum, tungsten, molybdenum, rhenium, hafnium, etc.). The substrate is protected by a coating system comprising an aluminum-containing bond coat on the surface of the substrate and a ceramic coating bonded to the substrate by the bond coat. The bond coat, preferably an aluminide, is deposited so as to be substantially free of ruthenium, though ruthenium is present in the bond coat as a result of diffusion from the substrate into the bond coat.

Abstract: A process for producing a rotor, the rotor formed thereby, as well as turbines in which such a rotor is installed. The rotor is formed by casting an ingot to have first and second regions formed of different alloys that intermix during casting to define a transition zone therebetween. The ingot is forged to yield a rotor forging that contains axially-aligned first and second alloy regions and a transition zone therebetween. The effects of the transition zone can be mitigated by modeling the transition zone and then off-center machining the forging so that the axis of rotation of the machined monolithic rotor is more centrally located with respect to the transition zone.

Abstract: A process for repairing a compressor rear frame of a gas turbine engine. The process entails removing a seal flange from the inner casing wall of the frame to define an annular face on the casing wall, and fabricating a replacement flange to have an annular face with a radial width greater than the radial width of the annular face of the casing wall. The faces of the flange and wall are mated to form a joint, a penetration-enhancing flux is deposited adjacent the joint, and a single-pass gas tungsten arc welding operation is performed to form a root weldment that extends completely through the joint. The flux is then removed and a gas tungsten arc welding operation is performed to deposit a filler on the root weldment and form a second weldment that completely overlays but does not penetrate through the root weldment.

Abstract: An electron beam physical vapor deposition (EBPVD) apparatus for producing a coating material (e.g., a ceramic thermal barrier coating) on an article. The EBPVD apparatus generally includes a coating chamber that is operable at elevated temperatures and subatmospheric pressures. An electron beam gun projects an electron beam into the coating chamber through an aperture in a wall of the chamber and onto a coating material within a coating region defined within the chamber, causing the coating material to melt and evaporate. An article is supported within the coating chamber so that vapors of the coating material deposit on the article. The operation of the EBPVD apparatus is enhanced by the inclusion within the coating chamber of a second chamber that encloses the aperture so as to separate the aperture from the coating region. The second chamber is maintained at a pressure lower than the coating region.

Abstract: A protective overlay coating for articles used in hostile thermal environments, and more particularly a predominantly beta-phase NiAl intermetallic overlay coating for use as an environmental coating or as a bond coat for a thermal barrier coating deposited on the overlay coating. The overlay coating has inner and outer regions, with the inner region containing more chromium than the outer region. The lower chromium content of the outer region promotes the oxidation resistance of the overlay coating, while the higher chromium content of the inner region promotes the hot corrosion resistance of the coating interior. Under hot corrosion conditions, hot corrosion may attack the outer region, but further hot corrosion attack will substantially cease once the relatively high-chromium inner region of the overlay coating is encountered.

Abstract: A method of fabricating a test model of a gas turbine engine combustor dome, and the test model produced thereby. The method entails individually stamping a plurality of dome wall segments and first and second mounting band segments. Each wall segment comprises at least one cup between radially inward and outward edges of the wall segment, and an opening in the cup. At least one wall segment and its two corresponding mounting band segments are placed on a fixture that locates the opening of the wall segment, locates the first and second mounting band segments at the radially-inward and outward edges of the wall segment, and orients the wall segment to establish a dome angle of the fixtured dome assembly. The wall segment and mounting band segments are then joined while the fixtured dome assembly remains on the fixture to form at least a unitary sector of the test model.

Abstract: A coating and coating process for incorporating surface features on an air-cooled substrate surface of a component for the purpose of promoting heat transfer from the component. The coating process generally comprises depositing a first metallic coating material on the surface of the component using a first set of coating conditions to form a first environmental coating layer, and then depositing a second metallic coating material using a second set of coating conditions that differ from the first set, such that an outer environmental coating layer is formed having raised surface features that cause the surface of the outer environmental coating layer to be rougher than the surface of the first environmental coating layer.

Abstract: A coating system for an article comprising a substrate formed of a metal alloy that is prone to the formation of a deleterious secondary reaction zone (SRZ) as a result of containing more than three weight percent rhenium and at least one additional refractory metal. The coating system comprises an aluminum-containing overlay coating and a diffusion barrier coating between the overlay coating and the substrate. The diffusion barrier coating consists of, in atomic percent, about 20% to about 90% ruthenium, about 2% to about 60% chromium, optionally up to about 50% aluminum, optionally up to about 20% of a platinum-group metal, and the balance at least one of nickel, cobalt, and iron and incidental impurities. The diffusion barrier coating sufficiently inhibits diffusion of aluminum from the overlay coating into the substrate, such that the substrate remains essentially free of SRZ.

Abstract: A process of removing deposits from through-holes in a component, such as metallic bond coat and ceramic materials from cooling holes in an air-cooled gas turbine engine. The process is particularly effective in removing a TBC material deposited in a cooling hole of a component as a result of depositing a coating of the TBC material on a surface of the component, in which the deposit is removed from the cooling hole without damaging the cooling hole or the TBC coating surrounding the cooling hole on the coated surface of the component. A preferred feature is that the cooling hole, including the entrance to the hole at a surface of the component opposite the coated surface and the coating surrounding the exit of the hole at the coated surface, exhibits improved surface characteristics that increase the discharge coefficient of the cooling hole, as evidenced by an increase in the effective area of the cooling hole.

Abstract: A fiber reinforced composite article comprising a matrix and reinforcing fibers, and different operating temperature and stress combinations each across opposed surfaces and through the matrix, is made by first measuring each of the combinations. Then discrete regions, each extending completely through the surfaces and the matrix, are selected for each combination. Reinforcing fibers with strength greater than the stress in a selected region are disposed in each selected region, the strengths being different between regions responsive to the different measured combinations.

Abstract: A turbine engine shroud segment is provided with a radially outer surface including a pair of spaced apart, opposed first and second edge portion surface depressions, for example spaced circumferentially, having a seal surface shaped to receive, in a surface depression formed between assembled adjacent segments in a shroud assembly, or axially assembled adjacent segments and engine members, a radially outer fluid seal member. The depression portions of a shroud segment are joined with the radially outer surface of the shroud segment through an arcuate transition surface. Stresses generated during engine operation in the shroud material are reduced, enabling practical use of a low ductility material, for example a ceramic matrix composite. The edge portion surface depressions are provided with a first shape and the fluid seal member, disposed at the depression, is provided with a surface of a second shape matched in shape with the first shape.

Abstract: A coating material for a component intended for use in a hostile thermal environment. The coating material has a cubic microstructure and consists essentially of either zirconia stabilized by dysprosia, erbia, gadolinium oxide, neodymia, samarium oxide or ytterbia, or hafnia stabilized by dysprosia, gadolinium oxide, samarium oxide, yttria or ytterbia. Up to five weight percent yttria may be added to the coating material.

Abstract: A beta-phase NiAl overlay coating containing a dispersion of ceramic particles and a process for depositing the overlay coating. If the coating is used to adhere a thermal barrier coating (TBC), the TBC exhibits improved spallation resistance as a result of the dispersion of ceramic particles having a dispersion-strengthening effect on the overlay coating. The overlay coating contains at least one reactive element and is deposited so that the some of the reactive element deposits as the ceramic particles dispersed in the overlay coating.

Abstract: At least one shroud segment, floating axially independently of adjacent turbine engine shroud assembly members, includes a segment body comprising a radially outer surface and a radially outwardly projecting segment support that includes an axial support wall surface therein. The assembly includes a shroud hanger in axial juxtaposition with the segment support, and at least one axial support projection from the shroud hanger into the segment support at the support wall surface. The support projection supports the shroud segment releasably at the support wall surface sufficiently to enable relative axial movement of the shroud segment on the support projection independently of the shroud hanger and adjacent engine members.

Abstract: A process of rejuvenating a diffusion aluminide coating on a component. The rejuvenation process involves treating the coating with an aqueous solution of nitric acid and phosphoric acid until at least part of the additive layer of the coating has been removed, but the diffusion zone underlying the additive layer remains. The exposed surface of the component is then re-aluminized to deposit additional aluminum to build up the additive layer to a desired thickness. While potentially useful for a variety of situations, the process is particularly applicable to a diffusion aluminide coating that has been deposited on a component to have an excessively thick additive layer, and prior to the component being returned to service.

Abstract: A PVD process and apparatus (120) for depositing a coating (132) from multiple sources (110, 111) of different materials. The process and apparatus (120) are particulaity intended to deposit a beta-nickel aluminide coating (132) containing one or more elements whose vapor pressures are lower than NiAl. The PVD process and apparatus (120) entail feeding at least two materials (110, 111) into a coating chamber (122) and evaporating the materials (110, 111) at different rates from separate molten pools (114, 115) thereof. Articles (130) to be coated are suspended within the coating chamber (122), and transported with a support apparatus (118) relative to the two molten pools (114, 115) so as to deposit a coating (132) with a controlled composition that is a mixture of the first and second materials (110, 111).

Abstract: An electron beam physical vapor deposition (EBPVD) apparatus and a method for using the apparatus to produce a coating material (e.g., a ceramic thermal barrier coating) on an article. The EBPVD apparatus generally includes a coating chamber that is operable at elevated temperatures and subatmospheric pressures. An electron beam gun projects an electron beam into the coating chamber and onto a coating material within the chamber, causing the coating material to melt and evaporate. An article is supported within the coating chamber so that vapors of the coating material deposit on the article. The operation of the EBPVD apparatus is enhanced by the inclusion or adaptation of one or more mechanical and/or process modifications, including those necessary or beneficial when operating the apparatus at coating pressures above 0.010 mbar.

Abstract: A process of removing ceramic deposits from a surface hole in a component, a particular example being portions of a ceramic coating deposited on a surface of a component equipped with cooling holes. The process makes use of a pulsed Nd:YAG laser operated with parameters that avoid delamination, cracking or otherwise damaging a ceramic coating surrounding a cooling hole. The laser is operated to generate a laser beam that removes some of the ceramic deposit from the hole while a residual portion of the ceramic deposit remains surrounding the hole to define a surface opening.