The influence of material properties on the wear of abradable materials

Abstract

In aero-engines it is possible for the blades of the compressor, turbine or fan to incur into their casings. At these interfaces a lining of composite abradable material is used to limit damage to components and thereby sustain the efficiency and longevity of the engine as a whole. These composite materials must have good abradability and erosion resistance. Previously, the wear mechanisms at the contact between the blade and the coating have been characterized using stroboscopic imaging and force measurement on a scaled test-rig platform.This work is focused on the characterization of the wear mechanism for two different of abradable lining. The established stroboscopic imaging technique and contact force measurements are combined with sectioning of the abradable material in order to analyse the material`s response during the tests. A measure of the thermal properties and the resulting temperature of the linings during the test have also been made to further understand the effect of coating hardness.The wear mechanism, material response, contact force and thermal properties of the coating have been used to characterize the different material behaviour with different hardness. At low incursion rates, with a soft coating, the blade tip becomes worn after an initial adhesive transfer from the coating. Post-test sectioning showed blade material and significant compaction present in the coating. The harder coating produced adhesion on the blade tip with solidification observed in the coating. Thermal diffusivity measurements and modelling indicated that thermally driven wear observed was as a consequence of the increased number of boundaries between the metal and hBN phases present interrupting heat flow, leading to a concentration of surface heat. At higher incursion rates the wear mechanism is more similar between the coatings and a cutting mechanism dominates producing negligible adhesion and blade wear.

A Novel Image Segmentation Approach for Microstructure Modelling

“…Variation in wear behaviour is seen across the width of the rub track of the same scale as variation between the spray batches shown here [24]. Models made from 200 × 200 µm 2 images showed standard deviation in thermal conductivity results of between 46% and 66% of the mean value ( Figure 9).…”

“…For the AlSi hBN abradable a large over prediction is seen. Matějíček et al and others have noted that residual binder surrounds the hBN particles [14,23,24]. This isolates the hBN from the heat flow in the metal matrix.…”

Investigating the application of a honeycomb abradable lining in the turbine stage of an aero-engine

“…As previously introduced, this study is focused on how the abradable filler properties affect the wear mechanism between the fin tip and abradable. Additionally, according to previous research, the tip speed and incursion speed are two dominant parameters with respect to the wear mechanism but the incursion depth is not a dominant test parameter [9][10][11][12]. Therefore, all the tests are conducted with a tip speed of 200ms -1 and incursion speed of 62.1 ms -…”

“…A series of studies have also been undertaken to characterize the wear mechanism between an abradable lining and compressor blade using in-situ measurement techniques. These techniques have included stroboscopic imaging to analyse the adhesive transfer between the blade tips and lining [9], as well as contact force measurement [10], and have been used to investigate the effect of different blade tip treatments [11] and abradable hardness [12] on the wear mechanics. Compared to compressor blade tip and abradable interactions, limited studies are available with respect to sealing fins.…”

“…. It should be noted that the incursion speed is selected to represent the incursion rate of 0.2 m/pass that was used in previous research [10,12] and is aero-engine representative. The incursion depth for this study was set at 2500 m to ensure that the test duration is sufficient for collecting data that would allow full analysis of the wear mechanism.…”