Session: 18-06 Metallurgy, Coating and Repair II

Paper Number: 121771

121771 - Tribological Evaluation of Coatings for Air Foil Bearing Applications 

In the pursuit of environmentally and sustainable transportation strategies, proton-exchange membrane fuel cells (PEM-FC) e-machines have emerged as a promising technology to decarbonise powertrains especially in heavy-duty vehicles. Oil-free bearings, the so-called Air Foil Bearings (AFBs), are crucial to the robust operation of the turbomachinery of the PEM-FC e-engines by preventing the contamination of  the hydrogen fuel cell stack. At high rotational speeds of the PEM-FC e-machines, an air film is formed between the top foil of the AFB and the journal.  Once the shaft becomes airborne, the friction forces in the interface are minimal. However, during start-up and coast down of the PEM-FC e-machine (start/stop event), there is contact between the top foil of the AFB and the journal, which leads to high friction forces and durability concerns for the AFBs. The objective of this work is to identify the coating system that minimizes the friction forces and optimises the wear resistance for AFB applications. With this aim, tribological pin-on-disc tests were performed using coated Inconel discs and coated tool steel pins under room temperature conditions and at 150 ◦C.  Additionally,  the development of a test rig to measure the tribological performance of  coated AFBs under real life applications is discussed. In the pin-on-disc tests, the coated disc represented the top foil of the AFB while the coated pin represented the journal. Four solid lubricants were investigated for the discs, while two types of DLC coatings (monolithic and multilayer) were used for the pins. The worn surfaces have been investigated via microscopy and elemental analysis. The adhesion strength of the coatings was evaluated through indentation (VDI 3198) and scratch tests. The tribosystem of multilayer DLC against solid lubricant / metal composite coating afforded the lowest frictional response and friction stability compared to the other coating systems under evaluation.

Presenting Author: Eleftherios Iakovakis University of Manchester

Presenting Author Biography: TBC

Authors:

Eleftherios Iakovakis University of Manchester
Sepideh Aliasghari University of Manchester
Philip Bonello University of Manchester
Allan Matthews University of Manchester
Michael Burkinshaw Cummins
Simon Moore Cummins