Characterization of Residual Stresses in Compressor Discs for Aeroengines

Abstract

Structural aeroengine components like forged high-pressure compressor discs are usually made of nickel-based superalloys due to their excellent high-temperature properties. [1] Especially Inconel 718 (IN718) is very widespread because of its excellent strength at elevated temperatures in combination with good fatigue and creep properties. [2] The specific performance of IN718 can mostly be attributed to the fine, semi-coherent c² precipitates, which act as a strengthening phase within the nickel matrix. c² is formed during a twostep aging sequence [3] which is performed after forging and before machining to final geometry. As dislocations represent potential nucleation sites for c² precipitates, rapid quenching to freeze dislocations increases the number of precipitates formed during the annealing cycle and, therefore, lead to a higher final strength. This optional heat treatment route which involves water quenching from the forging temperature, instead of solution annealing and subsequent air cooling, is referred to as ªdirect agingº. [4] However, water quenching leads to high residual stresses within the components. Although quenching is followed by the final aging treatment (with subsequent air cooling), residual stresses are not completely relieved. Therefore, heavy distortions of the forged component during machining to its final shape are still observed. These can lead to non-correctable deviations from COMMUNICATIONS

Diffraction‐Based Residual Stress Analysis Applied to Problems in the Aircraft Industry

“…[8] While the simulation produced good residual stress predictions for the disc, the results were not as good for the thin plate. Therefore, optimization of h(T) for the thin plate can still lead to a significant improvement of the simulation.…”

Characterization of Plastic Flow Pertinent to the Evolution of Bulk Residual Stress in Powder-Metallurgy, Nickel-Base Superalloys

“…Equations [6] and [7] were applied for fine (d c¢ 160 nm) and coarse (d c¢~2 60 nm) secondary-gammaprime precipitates in LSHR at 1144 K (871°C), at which f~0.43, E~165 GPa, m~0.3, and b~0.25 nm. Taking M = 3.06 (representative of a recrystallized superalloy with an fcc crystal structure of randomly oriented grains [30] ), the upper-bound flow stress due to precipitates was estimated as 750 and 460 MPa for the fine and coarse precipitates, respectively.…”

“…[3][4][5][6][7][8][9] In addition to part geometry, initial temperature, and orientation relative to the quench medium, inputs to such models include the thermophysical properties of the part/quench medium, interface heat transfer coefficients, and the constitutive response of the workpiece, each of which must be input as a function of temperature.…”

In‐Situ X‐ray Diffraction as a Tool to Probe Mechanical Phenomena Down to the Nano‐Scale

“…The cells are composed of 32±43 % partly crystalline and helically arranged cellulose, and a non-crystalline matrix consisting of 40±45 % lignin, and pectin. [26] Coir exhibits mechanical properties such as high fracture strain and toughness, and therefore represents an interesting biological model system with a relatively high average MFA of about 45 degrees. The fibre in Figure 4(a) was repeatedly loaded and unloaded and the structural changes were recorded by a 2D detector.…”