Comparative Study of Wc-20cr3c2-7ni and Al2o3-Tio2 Ceramic Coatings Prepared by Hvof or Aps Technology on the Salt Spray Corrosion

Abstract

Coating technologies are pivotal in protecting seawater service components, like ship valves, from corrosion. While the commonly used oxide coating is economical, its adhesion and toughness are suboptimal. In response, tungsten carbide (WC) based coatings, known for their superior toughness, have gained popularity. This paper conducts a comparative analysis of the salt spray corrosion resistance of two ceramic coatings. Using tin bronze as the substrate, Al2O3-40% TiO2 ceramic coatings were produced through Atmospheric Plasma Spraying (APS). Furthermore, two variations of WC-20Cr3C2-7Ni ceramic coatings were developed: one via High Velocity Oxygen Fuel (HVOF) and the other using APS. The test results show that the quality of HVOF-sprayed WC-20Cr3C2-7Ni coating is the best. Structural analysis revealed that the HVOF-sprayed WC-20Cr3C2-7Ni coating, characterized by low porosity and an absence of microcracks, exhibited the highest hardness and fracture toughness, with values of 574.02HV0.3 and 3.83 MPa·m1/2, respectively. Both the Al2O3-40%TiO2 and APS-sprayed WC-20Cr3C2-7Ni coatings showed the presence of cracks and pores, particularly pronounced in the latter, owing low toughness as well. In salt spray corrosion tests conducted over 10 and 20 days, The HVOF-sprayed WC-20Cr3C2-7Ni coating has the best corrosion performance, followed by the APS-sprayed Al2O3-40%TiO2 coating, with the APS-sprayed WC-20Cr3C2-7Ni coating worst. Both APS-sprayed Al2O3-40%TiO2 and APS-sprayed WC-20Cr3C2-7Ni coatings exhibited surface and internal corrosion media penetration, especially the latter, unlike the HVOF-sprayed WC-20Cr3C2-7Ni coatings, which remained impervious to corrosion.

Keywords: ceramic coating, Thermal spraying, Salt spray corrosion, Tin bronze, APS, HVOF