Periodic Reporting for period 2 - SUPERMODEL (Development and verification of microstructure, residual stress and deformation simulation capability for additive free-form direct deposition using multiple superalloys)
Berichtszeitraum: 2020-08-01 bis 2021-10-31
Laser Metal Deposition (LMD) is an additive manufacturing (AM) and repair technology that has evolved out of conventional laser cladding. As an additive technology, LMD has developed rapidly in the last decade, demonstrating significant potential to reduce costs and lead times for high quality, safety critical aerospace components. This potential can be realised through the reduction of tooling costs and increased material utilisation, both of which have a demonstrable impact on carbon footprint and waste in manufacturing.
Superalloys, such as Inconel 718 (IN718), have an impressive combination of mechanical properties, reliability at high temperatures, and low cost. Superalloys have been increasingly used in several applications, such as in gas turbines as well as in nuclear, oil & gas industries and cryogenic structures due to its excellent strength and aqueous corrosion resistances at low temperatures.
The thin-wall nature of aeroengine components makes LMD an attractive technology; however, there are many factors which affect the final quality and integrity of LMD parts, including the feedstock characteristics, process parameters, geometry, and subsequent heat treatments that are performed. In particular, the temperature transients that LMD parts experience involves rapid solidification, cyclic re-heating, and the potential build-up of heat in previously deposited layers. As a consequence, it is well-known that LMD parts may often exhibit unacceptable levels of distortion and residual stress, as well as unfavourable microstructural features including anisotropy; the precipitation of Laves and delta phases; and the segregation of alloying elements. These features can be removed with specially-designed heat treatments; however, identification of the correct heat treatments requires knowledge of the phase constitution in the part.
SUPERMODEL aims to develop a multi-scale model that links microstructural features to process parameters for laser additive manufacturing of superalloys. This will be achieved through a comprehensive and ambitious combined numerical-experimental programme of work. The overall objectives are to (1) develop and implement a microstructure model and associated process simulation for LMD of 718 and another superalloy; (2) establish and demonstrate a laboratory setup for capturing data to validate the model; (3) carry out a design-of-experiments approach involving the production, monitoring and characterisation of over 100 various samples; (4) validate the model and undertake additional activities on a more complex, multi-material build.
The project has demonstrated the feasibility and successful implementation of a thermo-mechanical-microstructural manufacturing process simulation for LMD of alloy 718 and another superalloy. The validation of the thermal model was within 5%, the distortion and residual stress predictions were within 10% of physical measurements, and the microstructure predictions were within 15% (although more accurate for individual microstructure constituents on the whole).
Superalloys, such as Inconel 718 (IN718), have an impressive combination of mechanical properties, reliability at high temperatures, and low cost. Superalloys have been increasingly used in several applications, such as in gas turbines as well as in nuclear, oil & gas industries and cryogenic structures due to its excellent strength and aqueous corrosion resistances at low temperatures.
The thin-wall nature of aeroengine components makes LMD an attractive technology; however, there are many factors which affect the final quality and integrity of LMD parts, including the feedstock characteristics, process parameters, geometry, and subsequent heat treatments that are performed. In particular, the temperature transients that LMD parts experience involves rapid solidification, cyclic re-heating, and the potential build-up of heat in previously deposited layers. As a consequence, it is well-known that LMD parts may often exhibit unacceptable levels of distortion and residual stress, as well as unfavourable microstructural features including anisotropy; the precipitation of Laves and delta phases; and the segregation of alloying elements. These features can be removed with specially-designed heat treatments; however, identification of the correct heat treatments requires knowledge of the phase constitution in the part.
SUPERMODEL aims to develop a multi-scale model that links microstructural features to process parameters for laser additive manufacturing of superalloys. This will be achieved through a comprehensive and ambitious combined numerical-experimental programme of work. The overall objectives are to (1) develop and implement a microstructure model and associated process simulation for LMD of 718 and another superalloy; (2) establish and demonstrate a laboratory setup for capturing data to validate the model; (3) carry out a design-of-experiments approach involving the production, monitoring and characterisation of over 100 various samples; (4) validate the model and undertake additional activities on a more complex, multi-material build.
The project has demonstrated the feasibility and successful implementation of a thermo-mechanical-microstructural manufacturing process simulation for LMD of alloy 718 and another superalloy. The validation of the thermal model was within 5%, the distortion and residual stress predictions were within 10% of physical measurements, and the microstructure predictions were within 15% (although more accurate for individual microstructure constituents on the whole).
The activities performed during the first reporting period concerned the numerical modelling (WP2) and experimental production of samples (WP3) to calibrate and validate the model. The activities performed during the second reporting period concerned the model validation and manufacture of more geometrically complex components.
As part of the numerical modelling activities in WP2, TWI developed and implemented a thermo-mechanical-metallurgical modelling capability that enables computer-based predictions of the link between process parameters and microstructure, defect density distributions, and residual stress for IN718 and another superalloy. The material model was calibrated and validated against the experimental data produced in WP3. In WP3, over 100 single-wall on plates specimens were produced. The test specimens were monitored during production (in-line monitoring); off-line inspected (CT scanning); and destructively examined (residual stress measurements, metallographic examination, X-ray Diffraction, EDS, and hardness maps) along different principal planes of the build and at different build heights. In WP4, branched builds were manufactured. The complexity of these builds manifested through the challenging tool path and deposition strategies as well as the large volume of material that led to the accumulation of heat, resulting in often small allowable processing windows. Although these challenges led to a significant amount of trial-and-error experimentation, the previously validated model was useful to provide insights into process conditions that would be successful. Finally, in WP5 a complex, multi-material demonstrator was built that featured curvature and additive aspects onto the cylindrical body. For all manufacturing activities, detailed thermal data was collected, oftentimes real-time strain data was collected, and the parts were metallographically examined with hardness maps, EBSD, optical microscopy, and further heat treatment studies were undertaken as well.
The dissemination of the project results was interrupted by the COVID-19 situation which led to several cancellations of conferences. However, the results were disseminated at a number of events towards the end of the project such as follows: (1) TWI annual Additive Manufacturing Symposium held in November 2019 with over 150 attendees; (2) TWI annual Japan Symposium with more than 100 in attendance; (3) an event hosted by the Japan National Institute of Materials Science in January2020. Other events include the following: The FESI Additive Manufacturing event October 2020; The NAFEMS Seminar entitled “How much validation is enough?”; An EPSRC Event in October 2021 on DfAM considering manufacturing process simulations; the 2021 TWI Annual AM Symposium Nov 2021; an ANSYS Materials Challenges event (October 2021).
In terms of exploitation, the project developed a novel integrated moving heat source to allow for time-scaling in AM simulations that has been used in commercial projects to provide streamlined and efficient simulations.
As part of the numerical modelling activities in WP2, TWI developed and implemented a thermo-mechanical-metallurgical modelling capability that enables computer-based predictions of the link between process parameters and microstructure, defect density distributions, and residual stress for IN718 and another superalloy. The material model was calibrated and validated against the experimental data produced in WP3. In WP3, over 100 single-wall on plates specimens were produced. The test specimens were monitored during production (in-line monitoring); off-line inspected (CT scanning); and destructively examined (residual stress measurements, metallographic examination, X-ray Diffraction, EDS, and hardness maps) along different principal planes of the build and at different build heights. In WP4, branched builds were manufactured. The complexity of these builds manifested through the challenging tool path and deposition strategies as well as the large volume of material that led to the accumulation of heat, resulting in often small allowable processing windows. Although these challenges led to a significant amount of trial-and-error experimentation, the previously validated model was useful to provide insights into process conditions that would be successful. Finally, in WP5 a complex, multi-material demonstrator was built that featured curvature and additive aspects onto the cylindrical body. For all manufacturing activities, detailed thermal data was collected, oftentimes real-time strain data was collected, and the parts were metallographically examined with hardness maps, EBSD, optical microscopy, and further heat treatment studies were undertaken as well.
The dissemination of the project results was interrupted by the COVID-19 situation which led to several cancellations of conferences. However, the results were disseminated at a number of events towards the end of the project such as follows: (1) TWI annual Additive Manufacturing Symposium held in November 2019 with over 150 attendees; (2) TWI annual Japan Symposium with more than 100 in attendance; (3) an event hosted by the Japan National Institute of Materials Science in January2020. Other events include the following: The FESI Additive Manufacturing event October 2020; The NAFEMS Seminar entitled “How much validation is enough?”; An EPSRC Event in October 2021 on DfAM considering manufacturing process simulations; the 2021 TWI Annual AM Symposium Nov 2021; an ANSYS Materials Challenges event (October 2021).
In terms of exploitation, the project developed a novel integrated moving heat source to allow for time-scaling in AM simulations that has been used in commercial projects to provide streamlined and efficient simulations.
The outcomes of the project will lead to a number of innovations above and beyond the current state-of-the-art. The outcomes of the project will lead to a number of innovations which include: (1) An integrated suite of self-consistent microstructural prediction tools derived from physics-based equations, empirical measurements and phenomenological models that runs within a part-level process simulation; (2) Extensive DoE measurement datasets to enable improved empirical understanding of LMD processing; and (3) a new in silico approach for process window optimisation for LMD of IN718 and another superalloy, therefore improving the time-to-market of these designs by improving quality assurance of their builds.
SUPERMODEL contributes to the aims of the Clean Sky Engines ITD by providing experimental data and simulation tools that will enhance the reliability of additive manufacturing technology, thereby streamlining LMD part certification and qualification, minimises experimental trial-and-error along the way. SUPERMODEL will therefore make progress towards achieving the EC goal of moving from “Modelling-for-Industry” to “Modelling-by-Industry” which means shifting effort from laboratory- and RTO-centred activities to helping industry equip itself with advanced simulation tools.
SUPERMODEL contributes to the aims of the Clean Sky Engines ITD by providing experimental data and simulation tools that will enhance the reliability of additive manufacturing technology, thereby streamlining LMD part certification and qualification, minimises experimental trial-and-error along the way. SUPERMODEL will therefore make progress towards achieving the EC goal of moving from “Modelling-for-Industry” to “Modelling-by-Industry” which means shifting effort from laboratory- and RTO-centred activities to helping industry equip itself with advanced simulation tools.