Formation of Surface Deposits on Steel and Titanium Aviation Fuel Tubes under Real Operating Conditions

Area of Science:

• Materials Science
• Aerospace Engineering
• Tribology

Background:

• Turbofan engines accumulate pyrolytic coke on internal components.
• Material degradation due to coke deposition impacts engine performance and lifespan.
• Stainless steel and titanium alloys are critical materials in engine construction.

Purpose of the Study:

• To compare pyrolytic coke deposition on stainless steel and titanium tubes from end-of-life turbofan engines.
• To analyze the influence of coke on the base materials.
• To investigate the effectiveness of ultrasonic cleaning for deposit removal.

Main Methods:

• Microhardness and topographical evaluations.
• Optical Emission Spectrometry (OES).
• Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX).
• Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS).

Main Results:

• Stainless steel exhibited thick pyrolytic coke layers containing carbon, oxygen, fuel, and additive elements.
• Ultrasonic cleaning removed most deposits, but carbon-rich patches remained on steel.
• Titanium surfaces had thinner coke layers and a ∼3 μm oxide layer from fuel additives, preventing extensive coke deposition.

Conclusions:

• Titanium's properties, including its TiO2 layer, promote different deposition mechanisms, preventing severe coke buildup seen on stainless steel.
• Material selection influences resistance to pyrolytic coke formation and degradation.
• Further research into surface properties and cleaning methods is warranted.