Rolls-Royce Holdings

About: Rolls-Royce Holdings is a company organization based out in Derby, United Kingdom. It is known for research contribution in the topics: Turbine & Gas compressor. The organization has 4027 authors who have published 6305 publications receiving 80517 citations. The organization is also known as: Rolls-Royce Holdings plc.

The oxidation characteristics of the nickel-based superalloy, RR1000, at temperatures of 700–900°C

Abstract: The oxidation kinetics are presented for a coarse-grained RR1000 alloy in the temperature range 700 – 900°C for times up to approximately 100 hours. The tests were undertaken in laboratory air in thermo-balances. The kinetics tended to sub-parabolic but were treated as parabolic to allow comparison with literature data. These parabolic rate constants were appreciably higher than expected for the growth of a protective oxide layer but were similar to those found previously on other Cr-rich Ni-based superalloys. SEM and confocal microscopy were used to show that the regions of emergent grain boundaries on the alloy surface oxidised faster than the grain centres. The surface oxide formed was Cr-rich with an enhancement of titanium in its outer regions. This is the situation at the grain boundaries and over the grain centres. Sub-surface oxidation of aluminium was observed, principally as intergranular fingers but also as intragranular particles. Ahead of this internal oxidation zone, at least for the...

The Effect of Strain Distribution on Microstructural Developments during Forging in a Newly Developed Nickel Base Superalloy

Abstract: In the current study, the effect of strain distribution in a simple forging geometry on the propensity for recrystallization, and its impact on mechanical properties has been investigated in a newly developed experimental nickel-based superalloy. The new alloy was produced via a Powder Metallurgy (PM) route and was subsequently Hot Isostatic Processed (HIP), isothermally forged, and heat treated to produce a coarse grain microstructure with average grain size of 23–32 μm. The alloy was examined by means of Electron Back-Scatter Diffraction (EBSD) to characterise the microstructural features such as grain orientation and morphology, grain boundary characteristics and the identification of potential Prior Particle Boundaries (PPBs) throughout each stage of the processing route. Results at the central region of the cross-section plane parallel to the loading direction showed significant microstructural differences across the forging depth. This microstructural variation was found to be highly dependent on the value of local strain imparted during forging such that areas of low effective strain showed partial recrystallisation and a necklace grain structure was observed following heat treatment. Meanwhile, a fully recrystallised microstructure with no PPBs was observed in the areas of high strain values, in the central region of the forging.

The microstructure of sigma 1140+SiC fibres

Abstract: Transmission electron microscopy (TEM) studies have been carried out on ‘as-received’ SM1140 + SiC fibres grown by CVD onto W wire cores. The transition between the W core and the SiC deposit is not abrupt in that there is a reaction zone present at the interface which actually consists of a silicide layer and a carbide layer. The SiC is subdivided into four concentric layers across the fibre diameter, each with a different morphology. The possible causes for the differences in the SiC morphology are discussed.

Gamma Prime Precipitate Evolution During Aging of a Model Nickel-Based Superalloy

Abstract: The microstructural stability of nickel-based superalloys is critical for maintaining alloy performance during service in gas turbine engines. In this study, the precipitate evolution in a model polycrystalline Ni-based superalloy during aging to 1000 hours has been studied via transmission electron microscopy, atom probe tomography, and neutron diffraction. Variations in phase composition and precipitate morphology, size, and volume fraction were observed during aging, while the constrained lattice misfit remained constant at approximately zero. The experimental composition of the γ matrix phase was consistent with thermodynamic equilibrium predictions, while significant differences were identified between the experimental and predicted results from the γ′ phase. These results have implications for the evolution of mechanical properties in service and their prediction using modeling methods.

Separation and Transition Control on an Aft-Loaded Ultra-High-Lift LP Turbine Blade at Low Reynolds Numbers: Low-Speed Investigation

Abstract: An experimental study was conducted to improve the performance of an aft-loaded ultra-high-lift low-pressure turbine blade known as U2 at low Reynolds numbers. This was achieved by manipulation of the laminar-turbulent transition process on the suction surface. The U2 profile was designed to meet the targets of reduced cost, weight and fuel burn of aircraft engines. The studies were conducted on both low-speed and high-speed experimental facilities under the unsteady flow conditions with upstream passing wakes. The current paper presents the low-speed investigation results. On the smooth suction surface, the incoming wakes are not strong enough to suppress the separation bubble due to the strong adverse pressure gradient on the suction surface and the low wake passing frequency, which allows the separation between the wakes more time to re-establish. Therefore, the profile losses of this ultra-high-lift blade are not as low as conventional or high-lift blades at low Reynolds numbers even in unsteady flows. Two different types of passive separation control devices, i.e. surface trips and air jets, were investigated to further improve the blade performance. The measurement results show that the profile losses can be further reduced to the levels similar to those of the high-lift and conventional blades due to the aft-loaded nature of this ultra-high-lift blade. Detailed surveys of the blade surface boundary layer developments showed that the loss reduction was due to the suppression of the separation underneath the wakes, the effect of the strengthened calmed region and the smaller separation bubble between wakes.Copyright © 2005 by ASME