Microstructure and Properties Transformation of Ni-C Coatings after Acid Salt Spray Corrosion
Ni-C abradable seal coatings were prepared by thermal spraying,and subjected to acid salt spray corrosion treatment for 192 hours.The microstructure,hardness,bonding strength,and abradability of Ni-C coatings before and after acid salt spray corrosion were explored.The research results indicate that the corrosion zone with thickness of 200-300 μm is formed on the top of Ni-C coatings after acidic salt spray corrosion.The average hardness of Ni-C coatings increases from(34.4±3.2)HR15 Y to(41.1±2.4)HR15 Y,and the average bonding strength of Ni-C coatings decreases from(14.6±0.7)MPa to(13.3±0.6)MPa.This is mainly due to the loss of soft materials such as graphite on the surface during the acidic salt spray corrosion,which leads to an increase in the surface average hardness.The poor bonding strength between the corrosion zone and uncorroded coating results in a decrease in bonding strength.The hardened corrosion layer is prone to peeling off during the wear-resistant scraping process,avoiding aggravating wear of dual blades due to the increased hardness of coating.The wear mechanism of the Ni-C coatings has not undergo significant change,remaining a mixed wear mechanism of plastic deformation and adhesive wear.
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