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Development and validation of a powder HIP route for high temperature Astroloy to manufacture Ultrafan® IP Turbine Casings

Periodic Reporting for period 1 - HUC (Development and validation of a powder HIP route for high temperature Astroloy to manufacture Ultrafan® IP Turbine Casings)

Reporting period: 2018-10-01 to 2020-03-31

The continued demand for improved gas turbine engine efficiency stimulates the constant development and application of higher performance materials. The higher the turbine inlet temperature, the higher the efficiency and lower emission of greenhouse effect gases. Hence, the gas turbine engines are affected by a demand to increase their operating temperatures, which is typically limited by the materials used. Ni-base superalloys are commonly used in aircraft engines due to their exceptional combination of high temperature strength, toughness, and great corrosion and oxidation resistance.

High γ’ volume fraction are desirable for high temperature applications. Astroloy with high amount of Al and Ti, which are linked with formation of γ´, Ni3(Al,Ti), is very interesting materials for more efficient engines. However, the vast presence of γ’ precipitates in this material make very difficult the manufacturing process by conventional cast and wrought route. Thus, new routes based on powder such as additive manufacturing (AM) or powder + hot isostatic pressing (HIP) processes are potential choices. Although AM technologies offer benefits from the manufacturing standpoint, the deposited material shows low ductility compromising the containment capacity of the casing. Instead, powder + HIP is more promising technique, in fact, HIP + forging route is the standard manufacturing route for high temperature discs with Ring Rolling as the naturally competitive choice. High temperature powder HIPped materials are less susceptible to being forged in the inherently non isothermal conditions under which Ring Rolling occurs. This together with the higher comparatively raw material costs (powder vs billet) would further challenge the competitiveness of any powder HIP + Forging based solution.

Consequently, Powder HIP without subsequent Forging could be a competitive solution for high temperature casing manufacturing route although this technique presents several challenges.

Thus, the main objective of HUC is to develop and validate a powder HIP manufacturing route for Astroloy that will improve the buy to fly ratio through Near Net Shape HIP, being the material developed able to withstand engine relevant conditions guaranteeing its ability to contain. Project has 8 technological objectives:

1: Development and Optimisation of a powder HIP processing route for a high temperature material.

2: Characterisation of mechanical properties to generate a database which supports the component design.

3: Development of experiments and numerical simulations to assess the material´s behaviour under dynamic and ballistic conditions.

4: Characterisation and understanding of mechanical properties with exposure at high temperatures.

5: Development of low cost tooling for HIPping high temperature superalloy casings.

6: Development and validation of process modelling capabilities.

7: Manufacturing of canning to guarantee the compliance of the finish product with the requirements.

8: Manufacturing of 3 full size IPT casings: 2 for real engine tests and 1 for NDTs.
Within the first 18 month of HUC project, 50 % of work have been completed.

WP1: Optimization and validation of the HIP route by means of depth microstructural characterisation and basic mechanical tests. Powder+HIP+Heat Treatment have been defined.

WP2: Mechanical tests to obtain material design data. Most of the material without exposure is already manufactured and sent to a Nadcap approved laboratory, Figure 1. Additionally, part of the exposed material has been already manufactured, other part is under ongoing exposure.

WP3: A material containment capacity model validation with ongoing ballistic tests and calibration of model parameter, Figure 2, is ongoing.

WP4: New HIP model has been developed incorporating viscoplastic mechanism and modifications of the shape of the pores during HIPping. A filling model have also been developed which incorporates the role of the powder particle characteristics and a phase diagram of vibrated powders.

WP5: Low-cost tooling manufacturing technique has been chosen. The design for the first demonstrator has been defined and its manufacturing is ongoing, Figure 3.

WP6: Three canning have been manufactured for full scale demonstrators. One of them has been already HIPped and machined (engine 1, see Figure 4) to the final product. Other two cannings are currently under powder feeling process.

WP7: NDT inspections and dimensional measurements for the different engine and demonstrator casings have been defined. First full scale engine casing was characterised before tooling removal and currently the characterization after the tooling removal is ongoing.

WP8: within the project management process, different press realise and conference and journal papers have been published and the project webpage have been created: http://huc-cs2.eu/
Progress beyond the state of the art:

HUC has gone a step further from the state of the art for powder-HIP process by using high quality tailored powders thanks to having a powder manufacturing company as a partner. In addition, a full process optimising has been carried out related to HIP parameters outgassing procedure and heat treatments.

In terms of HIP modelling, in HUC project both the DEM and the new CFD with powder apparent viscosity physical modelling have been applied and validated through experimental measurements, to develop a dedicated solution for reliable and robust simulation of real “big” industrial shapes capsule filling.

Until the end of the project HUC will contribute to create a database with mechanical property values onto Astroloy materials with exposure treatments.

A novel damage model based in combination of Johnson- Cook and Zerilli-Armstrong and including material thermal exposure effect will be developed to measure containment capacity for Astroloy.

The computational tools in HUC, to forecast distortions associated with HIP, will be a clear improvement on the status quo as they will also address the problem in an integral manner including capsule filling modelling, HIP process modelling and an algorithm for optimizing canister design.

HUC proposes a low cost process for canning manufacturing, that will significantly reduce the cost of NSHIPping.

Potential impacts:

An efficient raw material usage: more than 70 % against less than 15% of the traditional fabrication route; An efficient energy consumption: 80 % of energy savings by using NNSHIP instead of the traditional fabrication route; and 80% reduction of equivalent CO2 emission: due to the more efficient energy consumption the use of NNSHIP instead of traditional manufacturing route.
Figure 2-High fidelity simulation reproducing a ballistic impact test
Figure 1-Successfull HIPped canisters
Figure 3-Inner and outer manufactured by low-cost techniques
Figure 4-Final engine component