Self-lubricating, low-friction, wear-resistant Al-based quasicrystalline coatings

Area of Science:

• Materials Science
• Tribology
• Surface Engineering

Background:

• Developing advanced materials with self-lubricating properties is crucial for enhancing the durability and efficiency of mechanical components.
• Traditional self-lubricating materials often rely on soft additives that can degrade over time or be less effective under harsh conditions.
• Quasicrystalline materials exhibit unique properties that make them promising candidates for high-performance coatings.

Purpose of the Study:

• To develop and characterize a novel self-lubricating coating using quasicrystalline powder.
• To evaluate the wear resistance and friction performance of the developed coating.
• To investigate the microstructural features contributing to the coating's tribological behavior.

Main Methods:

• Gas atomization of an aluminum-based quasicrystalline powder.
• High-velocity oxygen-fuel (HVOF) flame torch spraying to create a thick coating on a bond-coat layer on a steel substrate.
• Post-spraying annealing treatment to stabilize the coating's phases.
• Pin-on-disk tribological testing to assess wear resistance and friction coefficient.

Main Results:

• The annealed coating consisted of a stable γ-brass crystal layer and an icosahedral quasicrystal.
• The coating demonstrated excellent wear resistance, with pin-on-disk test durations exceeding 5 km and negligible material loss.
• Low friction coefficients (µ ≤ 6% against sintered tungsten carbide) were achieved, outperforming the state of the art.
• Excellent substrate bonding via the bond coat and the presence of specific carbon coordination at quasicrystalline flake boundaries contributed to the tribological performance.

Conclusions:

• The developed quasicrystalline coating exhibits superior self-lubricating properties, characterized by high wear resistance and low friction.
• The coating's performance is attributed to its stable microstructure, robust substrate adhesion, and unique carbon-containing interfaces.
• This material holds significant potential for applications in hard materials for mechanical devices, offering extended operational life and reduced material waste by negating the need for soft lubricating additives.