Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - HiperTURB (Development of investment casting process of nickel superalloys with enhanced weldability.)

Teaser

H2020 Europe´s research and innovation program has identified as one key societal challenge the smart green and integrated transport. In this context the Clean Sky programme aims at developing and demonstrating competitive and environmentally friendly technology for the...

Summary

H2020 Europe´s research and innovation program has identified as one key societal challenge the smart green and integrated transport. In this context the Clean Sky programme aims at developing and demonstrating competitive and environmentally friendly technology for the aeronautic sector The Clean Sky2 ENGINES Integrated Technology Demonstrators (ITD) will demonstrate developed technologies at a whole engine level. Therefore, a set of new engine components have to be developed and manufactured, one of them is a Turbine Rear Frame (TRF).
The demands on reliability of this part are very high due to the combination of high thermal (around 700ºC) and structural loads. The main material characteristics to be considered are creep, mechanical properties at room and high temperature and weldability. During the engine lifetime cracking is major concern and TRF´s have to be inspected over time, overhauled, tested and repaired and this supposes not only a problem of enhanced costs, but also presents a mayor safety issue. Nowadays the alloys commonly used for the manufacturing of these parts are weldable nickel base superalloys.
It should be also noted that the TRF components and maintenance cost are an important issue as frames represent 16.3% of the total engine weight and around 15% of its total cost [1]. Furthermore, engine maintenance accounts for 35-40% of the total aircraft maintenance costs, (see section 2). Material replacements due to parts wear out represent about 60-70% of this percentage
In the HiperTURB project it is envisioned to improve weldability of a number of commercially available superalloys. This will be achieved by tailoring the solidification structure acting on the local cooling rate in the part (simulations tool, chillers, directional solidification etc.), performing inoculation and minor chemistry modifications, adapting the thermal processing and developing the welding process for the new alloys. Alloy and heat treatment development will be aided by microstructure simulation tools.

Work performed

The project has been running for 18 months. During this period, WP2 has been finished after 12 months period. Main results obtained during this period are the following ones:
• A deep analysis has been carried out of the effect of the different chemical elements in IN718 related to weldability.
• Innovative foundry, heat treatment and welding techniques and process adjustments have been analyzed completing the first analysis carried out in the state of the art of the proposal.
• Specific studies using the simulation software Thermocalc have been carried out obtaining a set of data valid for later on solidification modelling. These data have been also used as support for chemical elements selection in IN718 variants formulation.
• Supported in the data coming from deliverable D2.1 a preliminary trial plan has been defined and is currently under review as far as results of tasks carried out in other WP are conditioning its modification.

From month 1 to moth 18 WP3 has been running and main activities and results obtained during this period are described underneath.
• Test samples and a specific mold has been designed to contain all the samples and assuring the soundness of the specimens. The design has been validated by PROCAST simulations.
• The different IN718 variants have been selected as well as one alternative comercial alloy (ALLOY B).
• Samples have been manufactured following the standard process to be the base for comparison with the rest of the trials.
• Different microstructural parameters are under analysis to compare the different behavior of samples welding. Main parameters under analysis apart from chemical composition are grain size. carbides and laves phases quantification.
• Heat treatments carried out to the different samples have been studied in terms of grain size evolution but in next samples additional parameters such as chemical composition and laves phases will be included.
• Trials including inoculation have been carried out and compared at prototype level and are being scaled up to industrial equipments.

From month 1 to month 18 WP4 has been running and main activities and results obtained during this period are described underneath.
• Varestraint tests cross checking trials have been performed to assess reproducibility of results andcrack length measurement procedure.
• Tests have been carried out in the Varestraint machine for wrought and commercial IN718 castings. The effect of grain size (resulting from processing different types of samples) in TCL (Total crack length) has been investigated.
• Influence of welding technology and parameters on cracking susceptibility has been investigated including pulsed and continuous TIG and pulsed and continuous LBW.
• Automated vision analysis based on thermography images has been used as supporting tool to evaluate the TCL. Specific instructions have been developed to assure higher precision in terms of operator measuring technique reproducibility.

Final results

The ambition of this project is to improve the weldability and castability of high temperature capable superalloys by a novel manufacturing process. This novel process consist of a combination of innovative chemistry adjustments, tailored casting solidification and specific heat treatments to control grain size, phase formation, segregation and residual stresses.
In general the main industrial impacts of project results are related to:
i) The costs reduction in manufacturing process to be obtained by the reduction of rework needed in the casting and assembly welding process. HiperTURB expects to down by 10 % for TRF by the reduction of rework needed in the casting and assembly welding process, which impacts directly in aero engine OEMs and Tier1 profits (the total cost of poor quality in aircraft engines / engine parts is estimated between 5.4 and 6.3 % of sales ).
ii) The in-flight overhauling and repairing TRF cost reduction as far as nowadays only a 30% of the expected in life performance time is achieved. Aircraft Monitor’s 2011 report establishes that material replacement is the most significant item in engine maintenance. Typically, it can account for 60% - 70% of the engine’s direct maintenance cost . It is caused simply because parts wear out and have to be either replaced or repaired. A 20% engine maintenances cost reduction is expected, nowadays engine maintenance costs represents the 35% of the total aircraft’s maintenance cost (see Figure 2.5). This number is based on the development of robust and reliable TIG and laser based repairing techniques.
iii) The fuel consumption reduction due the possibility of performing more lightweight designs of TRF enabled by the use of higher perfomance Ni superalloys at around 700ºC and by the improvement of structural welds quality in castings. This has a big impact in operational costs of airlines.

Environmental impact:
1) Reduction of 30% of spare parts consumption rendering in around 30% less residues generation and natural resources savings. Even if it is less relevant, there is also a reduction of the amount of rework needed in the assembly welding process, and an expected weight reduction of the TRF component after the new achieved properties.
2) Reducing gaseous effluents and noise emissions (around 3%) in service thanks to future UHPE technology use in aircrafts. It affects the environmental impact of aircrafts during operation.

Website & more info

More info: http://www.azterlan.es.