Characterization of SLM-Manufactured Turbine Blade Microfeatures from Superalloy Powders

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel remains the material of choice for most hot gas path (HGP) components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings. Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of allowable maximum TIT, thereby impacting cycle efficiencies. Laser Additive Manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to produce designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex microfeatures in a mock turbine blade leading edge. Various cooling features are incorporated in design, consisting of internal impingement cooling, internal lattice structures, and external showerhead cooling. The internal structure is designed as a lattice of intersecting cylinders in order to mimic that of a porous material. Through a non-destructive approach, the presented design is analyzed against the departure of the design by utilizing X-ray computed tomography (CT). Employing this non-destructive testing (NDT) method, a more thorough analysis of the quality of manufacture is established by revealing the internal structures of the porous region and internal impingement array. Variance distribution between the design and manufactured test article are carried out for both internal impingement and external transpiration hole diameters from CT data. Flow testing is performed to characterize the uniformity of porous regions and flow behavior across the entire article for various pressure ratios. Discharge coefficients of internal impingement arrays and porous structures are quantified. A numerical model of fluid flow through the exact CAD geometry is analyzed over the range of experimental flowrates. By comparison of experimental and numerical data, performance discrepancies associated with manufacturing quality are observed. Simplifying assumptions to the domain are evaluated to compare predictions of CFD using the exact geometry. This study yields quantitative data on the build quality of the LAM process, providing more insight as to whether it is a viable option for manufacture of micro-features in current turbine blade production

Characterization Of Laser Additive Manufacturing-Fabricated Porous Superalloys For Turbine Components

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Lately, incremental performance gains responsible for increasing the allowable turbine inlet temperature (TIT) have been made mainly through innovations in cooling technology, specifically convective cooling schemes. Laser additive manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Through a nondestructive approach, the presented geometry is analyzed against the departure of the design by utilizing X-ray computed tomography (CT). Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Flow testing is performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficients of internal impingement arrays and engineered-porous structures are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for direct manufacture of microfeatures in current turbine blade production

Characterization Of Lam-Fabricated Porous Superalloys For Turbine Components

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel alloys remain the material of choice for most hot gas path components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings (TBC). Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of allowable maximum TIT, thereby impacting cycle efficiency capabilities. Laser Additive Manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Various cooling features were incorporated in the design, consisting of internal impingement cooling, internal lattice structures, and external showerhead or transpiration cooling. The internal structure was designed as a lattice of intersecting cylinders in order to mimic that of a porous material. Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Through a non-destructive approach, the presented geometry is further analyzed against the departure of the design by utilizing x-ray computed tomography (CT). Employing this non-destructive evaluation (NDE) method, a more thorough analysis of the quality of manufacture is established by revealing the internal structures of the porous region and internal impingement array. Flow testing was performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficient of internal impingement arrays and porous structure are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for manufacture of micro-features in current turbine blade production

Fabrication And Analysis Of Porous Superalloys For Turbine Components Using Laser Additive Manufacturing

This paper discusses the fabrication and manufacturing process of a simulated leading edge portion of a turbine blade with a porous superalloy structure constructed using Laser Additive Manufacturing (LAM) techniques. The LAM method was assessed based on its ability to successfully fabricate complex, porous structures within traditional turbine components. To simulate the manufacturing process, the leading edge was designed, fabricated, heat-treated and closely examined for manufacturing accuracy. Manufactured out of Inconel, the leading edge is a single piece which is capable of both internal and external cooling through the use of shower head cooling as well as with an internal cavity undergoing jet impingement cooling. The internal structure was designed as a lattice of intersecting holes in order to mimic that of a porous material. External hole geometry was measured to determine the accuracy and tolerances of the manufacturing process in order to analyze the hole uniformity over the leading edge portion of the blade. Flow testing was performed in order to characterize the effective flow area and uniformity at the exit of porous structures at multiple pressure ratios. The velocity field at the exit was measured and compared with the physical geometry in order to pinpoint manufacturing defects. The analysis outline yields quantitative data on the LAM process, providing insight as to whether or not it is a viable option for current turbine blade production

Fabrication And Analysis Of Porous Superalloys For Turbine Components Using Laser Additive Manufacturing

This paper discusses the fabrication and manufacturing process of a simulated leading edge portion of a turbine blade with a porous superalloy structure constructed using Laser Additive Manufacturing (LAM) techniques. The LAM method was assessed based on its ability to successfully fabricate complex, porous structures within traditional turbine components. To simulate the manufacturing process, the leading edge was designed, fabricated, heat-treated and closely examined for manufacturing accuracy. Manufactured out of Inconel, the leading edge is a single piece which is capable of both internal and external cooling through the use of shower head cooling as well as with an internal cavity undergoing jet impingement cooling. The internal structure was designed as a lattice of intersecting holes in order to mimic that of a porous material. External hole geometry was measured to determine the accuracy and tolerances of the manufacturing process in order to analyze the hole uniformity over the leading edge portion of the blade. Flow testing was performed in order to characterize the effective flow area and uniformity at the exit of porous structures at multiple pressure ratios. The velocity field at the exit was measured and compared with the physical geometry in order to pinpoint manufacturing defects. The analysis outline yields quantitative data on the LAM process, providing insight as to whether or not it is a viable option for current turbine blade production