This response to the call for proposals under the Clean Sky Joint Undertaking to manufacture static engine components from IN718 using Net Shape Hot Isostatic Pressing of powder (NSHIP) involved 3 partners with complementary expertise in the areas required to undertake the work including powder characterisation; NSHIP and modelling; low cost tooling, as well as microstructural and property assessment.
The NSHIP of powder has the potential to revolutionise the production of complex high-performance aerospace parts enabling significant improved buy-to-fly ratios which give cost savings as well as environmental benefits. To exploit this technology, significant challenges must be addressed including; difficulty in HIPping nickel super alloy powder, high cost of sacrificial tooling, diffused surface layer on components due to interaction with the tool material and finally the lack of credible performance information for IN718 parts produced using the NSHIP process. The partners used a rigorous and yet innovative approach to address these challenges in this 2-year collaborative project.
Trials were performed to determine the best powder and HIPping conditions to use to produce parts with the desired microstructure and properties. Novel low cost tooling methods were developed and surface engineering techniques, to eliminate tool/component interaction, were explored. A computation model of IN718 powder consolidation was used to calculate the correct tool geometry to enable “right-first-time” net shape parts to be produced. Finally, demonstration components and test sample were produced using the most appropriate powder and manufacturing parameters. Test samples were subjected to NADCAP-approved mechanical property testing. The quality of the demonstration components was assessed by the partners and subsequently supplied to ITP for long term evaluation.
The final result of Nesmonic project is a validated cost effective NSHIP manufacturing route for IN718 parts for aero-engine application. To obtain this result it has been necessary to optimise all steps of powder manufacturing route. Initially, a complete characterisation of IN718 powders has been done and in close collaboration with powder producers a powder with the optimum properties has been designed, produced in industrial atomisers and bought. It is mandatory to work with a material with the adequate tap density, interstitials content, chemical composition, morphology and price. After that, it was investigated an outgassing procedure to encapsulate the material without any modification of as-atomised powder properties. In addition, the optimisation of HIP and HT window was essential to successfully achieve the microstructural and mechanical requirements. Nesmonic project has been able to analyse and optimise all these steps and using the optimum experimental conditions, the OEM requirements initially stablished have been successfully achieved although toughness, measured by Charpy tests is smaller than for wrought IN718.
Moreover, the other main advantage of Nesmonic project is the cost benefit of the NSHIP approach. For this reason, many different tooling methods have been studied in the project couple with the use of computational modelling to ensure that net shape or near net shape parts were produced, reducing machining operations. After the analysis of the different tooling methods a complex mid-scale and large demonstrator component has been manufactured and characterised using the optimum tooling methods to demonstrate the ability of Nesmonic project to apply the manufacturing route proposed in the fabrication of a real engine part (Low Pressure Turbine casing).
Finally, additive manufacturing technique (AM) has been also used in the project to fabricate the canister needed for HIPping the IN718 powder and produce the small demonstrator component. This part has been an interesting opportunity to introduce AM technology in the fabrication of engine parts, knowing the current advantages and limitations of this technology and their solutions.
Therefore, the main impact of Nesmonic is in the area of manufacturing. The impact in manufacturing is in both the reduced cost and improved eco-efficiency of the manufacturing process which requires less material and energy input than current manufacturing methods based on forging and machining. The improved Inconel 718 powder, tooling methods, which have been developed in the project, coupled with the use of computational modelling to ensure that net shape parts are produced in the minimum number of iterations, have significant bearing on the overall cost benefit of the NSHIP approach.
In conclusion, the main impacts of this project are:
- Development of a new manufacturing route based on the Hot Isostatic Pressing (HIP) of In718 gas atomized powders able to successfully achieve the mechanical and microstructural requirements of the OEM.
- Significant reduction in raw material and energy consumption during manufacture and performance of high performance IN718 parts.
- Ability to manufacture complex components, with an optimum accuracy due to computational modelling used.