High-Temperature Corrosion Behavior of Selected HVOF-Sprayed Super-Alloy Based Coatings in Aggressive Environment at...

Area of Science:

• Materials Science
• Corrosion Engineering
• Surface Engineering

Background:

• Components in power equipment require robust materials for high-temperature applications.
• High-temperature corrosion significantly degrades material performance and lifespan.
• Thermally sprayed coatings offer a protective solution against harsh operational environments.

Purpose of the Study:

• To evaluate the high-temperature corrosion resistance of various thermally sprayed coatings.
• To compare the performance of NiCoCrAlYHfSi, NiCoCrAlY, NiCoCrAlTaReY, and CoCrAlYTaCSi coatings.
• To assess coating durability in a simulated coal-fired boiler molten salt environment.

Main Methods:

• Coatings were applied using High-Pressure/High-Velocity Oxygen Fuel (HP/HVOF) technology.
• Corrosion testing involved cyclic exposure to a 75% Na2SO4 and 25% NaCl molten salt mixture at 800 °C.
• Corrosion kinetics were determined by weight change measurements after each cycle.
• Microstructural analysis utilized optical microscopy (OM), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS).

Main Results:

• The CoCrAlYTaCSi coating exhibited the best corrosion resistance among all tested coatings.
• NiCoCrAlTaReY and NiCoCrAlY coatings also showed significant corrosion resistance.
• All evaluated thermally sprayed coatings outperformed reference P91 and H800 steels in the corrosive environment.

Conclusions:

• The CoCrAlYTaCSi coating is a highly effective material for mitigating high-temperature corrosion in power equipment components.
• Thermally sprayed coatings provide a viable and superior alternative to conventional steels in aggressive, high-temperature settings.
• Further research into the specific mechanisms of CoCrAlYTaCSi coating protection is warranted.