Development of light-weight steel castings for efficient aircraft engines - Summary report

This report summaries the work carried out in the project, LEAN - Development of light-weight steel castings for efficient aircraft engines. The overall object in the project was to develop thinner cast steel components for aircraft engines. The work was conducted in collaboration between research institutes and industry. Swerea SWECAST, the Swedish foundry institute, which has a long tradition in collaboration with the industry in research projects, was the project leader and leader in one of the work packages. FRI, the Polish Foundry Research Institute, which has advance equipment for material science and material data investigations, was the leader of the second work package. The investment foundry TPC Components AB conducted casting trials and contributed with their wide knowledge of investment casting. Casting trials have been performed in order to investigate the influence of different process parameters governing the fluidity of thin walled investment castings. The alloy used was CbCu7-1, i.e. the cast analogy of the stainless precipitation-hardening steel 17-4PH. Two levels of geometry complexity were used as well as top- and bottom gated casting systems. In the first trial, a blade thicknesses ranging from 0.7-2.0 mm was used. In the second trial, some features were added to the blade as well as a textured surface on one side. It was shown that the top gated casting system showed an overall improved fluidity compared to the bottom gated casting system for the simpler geometry. Blade thickness and pouring temperature were shown to have the greatest impact on fluidity. Adding some geometrical features to the simple geometry drastically decreased the differences between the filling systems. Using a one side textured blade with thickness of 1.3 and 1.5 mm was comparable with 1.5 and 2.0 mm flat castings thus reducing weight of the thinnest sections of a steel casting. Predictions of miss-runs with simulations were shown to be in good agreement with experiments and gave valuable insight to problems in the casting trials. Differences in porosity levels were seen between the top- and bottom gated casting systems for the simpler geometry at high metal temperatures, where the former showed a larger amount of porosity. Besides the work performed on fluidity of the cast analogy of 17-4PH, a number of other alloys not commonly used for castings today were evaluated in terms of their fluidity and were compared to 17-4PH. The casting trials were performed with a bar casting. It was shown that JETHETE 152M had the best fluidity followed by Custom 465, L0H12N4M and 17-4PH. CSS 42L and PH13-8M ranked worst in the fluidity comparison and were therefore excluded from further investigations. Mechanical testing at both ambient and elevated temperatures (400 degrees Celsius) was performed. It was concluded that JETHETE 152M was the best performing alloy with respect to mechanical properties, followed by L0H12N4M, 17-4PH and Custom 465. However, JETHETE 152M was later excluded due to its poor corrosion properties. In the corrosion test, at 400 degrees Celsius, for 100 hours with salt spray fog, it was determined that the 17-4PH and L0H12N4M showed similar corrosion rates. Wettability test performed on two different shell systems with 17-4PH showed that the shell/alloy system is important to consider during filling of thin sections. The 17-4PH alloy was used in the casting trials of a demonstrator. It was demonstrated during the casting trials that filling of a wide flat section with a thickness below 2 mm is hard to achieve