Abstract
Aubert&Duval has developed a methodology to establish a residual stress model for Inconel 718 engine discs. To validate the thermal, mechanical and metallurgical parts of the model, trials on lab specimens with specific geometry were carried out. These trials allow a better understanding of the residual stress distribution and evolution during different processes (quenching, ageing, machining). A comparison between experimental and numerical results reveals the residual stresses model accuracy. Aubert&Duval has also developed a mechanical properties prediction model. Coupled with the residual stress prediction model, Aubert&Duval can now propose improvements to the process of manufacturing in Inconel 718 engine disks. This model enables Aubert&Duval customers and subcontractors to anticipate distortions issues during machining. It could also be usedt to optimise the engine disk life.
Highlights
Aubert&Duval produces Inconel 718 disks for aerospace engines
In the case of engine disks made in Inconel 718, its heat treatment can consist of solutioning at 980 ◦C for 1 hour followed by water quenching and a double ageing at 720 ◦C and 620 ◦C for 8 hours respectively (Fig. 1)
For vapourisable media like water, quenching trials with thermocouples are necessary due to the complexity of the liquid flow and phase transformation [3]. These data are completed by evident progress made in Computational Fluid Dynamics (CFD)
Summary
The specifications of its customers define targets for mechanical properties (creep, tensile or fatigue) To achieve these challenging requirements, Aubert&Duval applies specific heat treatments. In the case of engine disks made in Inconel 718, its heat treatment can consist of solutioning at 980 ◦C for 1 hour followed by water quenching and a double ageing at 720 ◦C and 620 ◦C for 8 hours respectively (Fig. 1). While these heat treatments produce the required mechanical properties, high levels of residual stresses are generated when quenching is necessary. Metallurgical, mechanical properties and residual stress models are presented, coupled and applied to an Inconel 718 pancake representative of engine disks
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